Organic compounds

ABSTRACT

The present invention relates to a new use of phosphodiesterase 1 (PDE1) inhibitors for the treatment and/or prophylaxis of narcolepsy.

This application claims priority from U.S. Provisional Application No. 60/858,732, filed on Nov. 13, 2006, and U.S. Provisional Application No. 60/873,175, filed on Dec. 5, 2006, the contents of both of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a new use for compounds that inhibit phosphodiesterase 1 (PDE1), e.g., that inhibit PDE1-mediated suppression of the dopamine D1 receptor intracellular pathway, specifically for the treatment of narcolepsy.

BACKGROUND OF THE INVENTION

Narcolepsy is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles normally. At various times throughout the day, people with narcolepsy experience fleeting urges to sleep. If the urge becomes overwhelming, patients fall asleep for periods lasting from a few seconds to several minutes. In rare cases, some people may remain asleep for an hour or longer.

Narcoleptic sleep episodes can occur at any time, often without warning, and may be quite dangerous if patients are driving or operating machinery. In addition to daytime sleepiness, patients may experience cataplexy, or the sudden loss of voluntary muscle tone; vivid hallucinations during sleep onset or upon awakening; brief episodes of total paralysis at the beginning or end of sleep; and/or automatic behavior, such as talking or performing routine activities during a sleep episode but having no memory of these activities upon waking. Most patients also experience frequent awakenings during nighttime sleep. For these reasons, narcolepsy is considered to be a disorder of the normal boundaries between the sleeping and waking states.

Eleven families of phosphodiesterases (PDEs) have been identified but only PDEs in Family I, the Ca²⁺-calmodulin-dependent phosphodiesterases (CaM-PDEs), have been shown to mediate the calcium and cyclic nucleotide (e.g. cAMP and cGMP) signaling pathways. The three known CaM-PDE genes, PDE1A, PDE1B, and PDE1C, are all expressed in central nervous system tissue. PDE1A is expressed throughout the brain with higher levels of expression in the CA1 to CA3 layers of the hippocampus and cerebellum and at a low level in the striatum. PDE1A is also expressed in the lung and heart. PDE1B is predominately expressed in the striatum, dentate gyms, olfactory tract and cerebellum, and its expression correlates with brain regions having high levels of dopaminergic innervation. Although PDE1B is primarily expressed in the central nervous system, it may be detected in the heart. PDE1C is primarily expressed in olfactory epithelium, cerebellar granule cells, and striatum. PDE1C is also expressed in the heart and vascular smooth muscle.

Cyclic nucleotide phosphodiesterases downregulate intracellular cAMP and cGMP signaling by hydrolyzing these cyclic nucleotides to their respective inactive 5′-monophosphates (5′AMP and 5′GMP). CaM-PDEs play a critical role in mediating signal transduction in brain cells, particularly within an area of the brain known as the basal ganglia or striatum. For example, NMDA-type glutamate receptor activation and/or dopamine D2 receptor activation result in increased intracellular calcium concentrations, leading to activation of effectors such as calmodulin-dependent kinase (CaMKII) and calcineurin and to activation of CaM-PDEs, resulting in reduced cAMP and cGMP. Dopamine D1 receptor activation, on the other hand, leads to activation of calcium dependent nucleotide cyclases, resulting in increased cAMP and cGMP. These cyclic nucleotides in turn activate protein kinase A (PKA; cAMP-dependent protein kinase) and/or protein kinase G (PKG; cGMP-dependent protein kinase) that phosphorylate downstream signal transduction pathway elements such as DARPP-32 (dopamine and cAMP-regulated phosphoprotein) and cAMP responsive element binding protein (CREB).

CaM-PDEs can therefore affect dopamine-regulated and other intracellular signaling pathways in the basal ganglia (striatum), including but not limited to nitric oxide, noradrenergic, neurotensin, CCK, VIP, serotonin, glutamate (e.g., NMDA receptor, AMPA receptor), GABA, acetylcholine, adenosine (e.g., A2A receptor), cannabinoid receptor, natriuretic peptide (e.g., ANP, BNP, CNP) and endorphin intracellular signaling pathways.

Phosphodiesterase (PDE) activity, in particular, phosphodiesterase 1 (PDE1) activity, functions in brain tissue as a regulator of locomotor activity and learning and memory. PDE1 is a therapeutic target for regulation of intracellular signaling pathways, preferably in the nervous system, including but not limited to a dopamine D1 receptor, dopamine D2 receptor, nitric oxide, noradrenergic, neurotensin, CCK, VIP, serotonin, glutamate (e.g., NMDA receptor, AMPA receptor), GABA, acetylcholine, adenosine (e.g., A2A receptor), cannabinoid receptor, natriuretic peptide (e.g., ANP, BNP, CNP) or endorphin intracellular signaling pathway. For example, inhibition of PDE1B may potentiate the effect of a dopamine D1 agonist by protecting cGMP and cAMP from degradation, and similarly inhibit dopamine D2 receptor signaling pathways, by inhibiting PDE1 activity. PDE1 inhibitors are therefore potentially useful in diseases characterized by reduced dopamine D1 receptor signaling activity. See generally, WO 03/020702.

EP 0201188 and EP 0911333, the contents of which are incorporated herein by reference, disclose certain 1,3,5,-substituted, 6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one compounds, claimed to be useful for treatment of cardiovascular disease, erectile dysfunction, and other disorders. These compounds are not, however, taught or suggested to be useful for the treatment of diseases involving disorders of the dopamine D1 receptor intracellular pathway, particularly diseases relating to sleep disorders such as narcolepsy. PCT/US2006/33179, the contents of which are incorporated herein by reference, discloses the use of 1,3,5,-substituted, 6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one compounds for treatment of diseases involving disorders of the dopamine D1 receptor intracellular pathway, but does not specifically disclose the use of such compounds in the treatment or prophylaxis of narcolepsy. PCT/US2006/022066, the contents of which are incorporated herein by reference, discloses PDE1 inhibitors which are 7,8-dihydro-[1H or 2H]-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones or 7,8,9-trihydro-[1H or 2H]-pyrimido[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones, but does not specifically disclose their use for the treatment or prophylaxis of narcolepsy. WO 03/042216, U.S. Pat. No. 5,939,419, EP 0 538 332, U.S. Pat. No. 5,393,755, U.S. Pat. No. 6,969,719 B2, Xia et al., J. Med. Chem. (1997), 40, 4372-4377 and Aim et al., J. Med. Chem. (1997), 40, 2196-2210, the contents of all of which are incorporated herein by reference, disclose PDE1 cGMP phosphodiesterase inhibitors which are substituted pyrazolo[3,4-d]pyrimidine, pyrimido[2,1-b]purin-4-one and imidazo[2,1-b]purin-4-one analogues useful for the treatment of hypertensive, cardiovascular, sexual dysfunction and other cGMP-PDEV related disorders, but do not specifically disclose their use for the treatment or prophylaxis of narcolepsy.

SUMMARY OF THE INVENTION

The invention provides a new method of treatment or prophylaxis for narcolepsy comprising administering an effective amount of a phosphodiesterase-1 (PDE1) inhibitor to a patient in need thereof. PDE1 inhibitors include, for example, 7,8-dihydro-[1H or 2H]-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones or 7,8,9-trihydro-[1H or 2H]-pyrimido[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones, substituted at the 1 or 2 position with C₂₋₉ alkyl or C₃₋₉ cycloalkyl, or optionally substituted heteroarylalkyl or substituted arylalkyl, in free, salt or prodrug form (hereinafter a PDE 1 Inhibitor, e.g., as described below) or a 1,3,5-substituted 6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one, in free, salt or prodrug form (also included in PDE 1 Inhibitors, e.g., as described below), to a patient in need thereof.

PDE1 inhibitors also include, for example, substituted imidazo[2,1-b]purin-4-one, e.g., (6aR,9aS)-2-(biphenyl-4-ylmethyl)-5,6a,7,8,9,9a-hexahydro-5-methyl-3(phenylmethyl)-cyclopent-[4,5]imidazo-[2,1-b]purin-4(3H)-one, (6aR,9aS)-5,6a,7,8,9,9a-hexahydro-5-methyl-2,3-bis(phenylmethyl)cyclopent-[4,5]imidazo-[2,1-b]purin-4(3H)-one, 5′-methyl-2′,3′-bis(phenylmethyl)spiro[cyclopentane-1,7′(8′H)-[3H]imidazo[2,1-b]purin]-4′(5′H)-one, or 5′-methyl-2′-(biphenylylmethyl)-3′-(phenylmethyl)spiro[cyclopentane-1,7′(8′H)-[3H]imidazo[2,1-b]purin]-4′(5′H)-one as described in Ahn et al., J. Med. Chem. (1997), 40, 2196-2210 (hereinafter a PDE 1 Inhibitor, e.g., as described below). These compounds are found to selectively inhibit phosphodiesterase 1 (PDE1) activity, especially PDE1B activity, and to be useful in the treatment and prophylaxis of narcolepsy. These compounds are found to selectively inhibit phosphodiesterase 1 (PDE1) activity, especially PDE1B activity, and to be useful in the treatment and prophylaxis of narcolepsy.

DETAILED DESCRIPTION OF THE INVENTION Compounds for Use in the Methods of the Invention

Preferably, the PDE 1 Inhibitors for use in the methods of treatment described herein are a 7,8-dihydro-[1H or 2H]-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones or 7,8,9-trihydro-[1H or 2H]-pyrimido[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones, of formula I

wherein

-   -   (i) R₁ is H or C₁₋₄ alkyl (e.g., methyl);     -   (ii) R₄ is H or C₁₋₄ alkyl and R₂ and R₃ are, independently, H         or C₁₋₄ alkyl (e.g., R₂ and R₃ are both methyl, or R₂ is H and         R₃ is isopropyl), aryl, heteroaryl, (optionally         hetero)arylalkoxy, or (optionally hetero)arylalkyl;     -   or     -   R₂ is H and R₃ and R₄ together form a di-, tri- or         tetramethylene bridge (pref. wherein the R₃ and R₄ together have         the cis configuration, e.g., where the carbons carrying R₃ and         R₄ have the R and S configurations, respectively);     -   (iii) R₅ is a substituted heteroarylalkyl, e.g., substituted         with haloalkyl     -   or     -   R₅ is attached to one of the nitrogen atoms on the pyrazolo         portion of Formula I and is a moiety of Formula Q

wherein X, Y and Z are, independently, N or C, and R₈, R₉, R₁₁ and R₁₂ are independently H or halogen (e.g., Cl or F), and R₁₀ is halogen, alkyl, cycloalkyl, haloalkyl (e.g., trifluoromethyl), aryl (e.g., phenyl), heteroaryl (e.g., pyridyl (for example pyrid-2-yl), or thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl)), diazolyl, triazolyl, tetrazolyl, arylcarbonyl (e.g., benzoyl), alkylsulfonyl (e.g., methylsulfonyl), heteroarylcarbonyl, or alkoxycarbonyl; provided that when X, Y, or Z is nitrogen, R₈, R₉, or R₁₀, respectively, is not present; and

-   -   (iv) R₆ is H, alkyl, aryl, heteroaryl, arylalkyl (e.g., benzyl),         arylamino (e.g., phenylamino), heteroarylamino,         N,N-dialkylamino, N,N-diarylamino, or N-aryl-N-(arylalkyl)amino         (e.g., N-phenyl-N-(1,1′-biphen-4-ylmethyl)amino); and     -   (v) n=0 or 1;     -   (vi) when n=1, A is —C(R₁₃R₁₄)—     -   wherein R₁₃ and R₁₄, are, independently, H or C₁₋₄ alkyl, aryl,         heteroaryl, (optionally hetero)arylalkoxy or (optionally         hetero)arylalkyl;         in free, salt or prodrug form, including its enantiomers,         diasterisomers and racemates.

The invention further provides the use of PDE 1 Inhibitors of Formula I as follows:

-   -   1.1 Formula I wherein R₁ is methyl and n=0;     -   1.2 Formula I or 1.1 wherein R₄ is H or C₁₋₄ alkyl and at least         one of R₂ and R₃ is lower alkyl, such that when the carbon         carrying R₃ is chiral, it has the R configuration, e.g., wherein         both R₂ and R₃ are methyl, or wherein one is hydrogen and the         other isopropyl;     -   1.3 Formula I or 1.1 wherein R₄ is H and at least one of R₂ and         R₃ is arylalkoxy;     -   1.4 Formula I wherein R₁ is methyl, R₂, R₃, and R₄ are H, n=1,         and R₁₃ and R₁₄ are, independently, H or C₁₋₄ alkyl (e.g.,         methyl or isopropyl);     -   1.5 Formula I or 1.1 wherein R₂ is H and R₃ and R₄ together form         a tri- or tetramethylene bridge, having the cis configuration,         preferably wherein the carbons carrying R₃ and R₄ have the R and         S configurations respectively;     -   1.6 Formula I, 1.1 or 1.5 wherein R₅ is a substituted         heteroarylmethyl, e.g., para-substituted with haloalkyl;     -   1.7 Formula I, 1.1, 1.2, 1.3, 1.4 or 1.5 wherein R₅ is a moiety         of Formula Q wherein R₈, R₉, R₁₁, and R₁₂ are H and R₁₀ is         phenyl;     -   1.8 Formula I, 1.1, 1.2, 1.3, 1.4 or 1.5 wherein R₅ is a moiety         of Formula Q wherein R₈, R₉, R₁₁, and R₁₂ are H and R₁₀ is         pyridyl or thiadiazolyl;     -   1.9 Formula I, 1.1, 1.2, 1.3, 1.4 or 1.5 wherein R₅ is a moiety         of Formula Q wherein R₈, R₉, R₁₁, and R₁₂ are, independently, H         or halogen, and R₁₀ is haloalkyl;     -   1.10 Formula I, 1.1, 1.2, 1.3, 1.4 or 1.5 wherein R₅ is a moiety         of Formula Q wherein R₈, R₉, R₁₁, and R₁₂ are, independently, H,         and R₁₀ is alkyl sulfonyl;     -   1.11 any of the preceding formulae wherein R₅ is attached to the         2-position nitrogen on the pyrazolo ring;     -   1.12 any of the preceding formulae wherein R₆ is benzyl;     -   1.13 any of the preceding formulae wherein R₆ is phenylamino or         phenylalkylamino (e.g., benzylamino);     -   1.14 any of the preceding formulae wherein R₆ is phenylamino;     -   1.15 any of the preceding formulae wherein X, Y, and Z are all         C,     -   1.16 any of the preceding formulae wherein X, Y, and Z are all C         and R₁₀ is phenyl or 2-pyridyl; and/or     -   1.17 any of the preceding formulae wherein the compounds inhibit         phosphodiesterase-mediated (e.g., PDE1-mediated, especially         PDE1B-mediated) hydrolysis of cGMP, e.g., with an IC₅₀ of less         than 1 μM, preferably less than 25 nM in an immobilized-metal         affinity particle reagent PDE assay, for example, as described         in Example 1;         in free or salt form.

For example, the PDE 1 Inhibitors include 7,8-dihydro-[1H or 2H]-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-ones of Formula Ia

wherein

-   -   (i) R₁ is H or C₁₋₄ alkyl [e.g., methyl];     -   (ii) R₄ is H and R₂ and R₃ are, independently, H or C₁₋₄ alkyl         [e.g., R₂ and R₃ are both methyl, or R₂ is H and R₃ is         isopropyl], aryl, or arylalkyl;     -   or R₂ is H and R₃ and R₄ together form a di-, tri- or         tetramethylene bridge [pref. wherein the R₃ and R₄ have the cis         configuration, e.g., where the carbons carrying R₃ and R₄ have         the R and S configurations respectively];     -   (iii) R₅ is attached to one of the nitrogen atoms on the         pyrazolo portion of formula Ia and is a substituted benzyl of         formula Qa

-   -   wherein R₈, R₉, R₁₁ and R₁₂ are independently H or halogen         (e.g., Cl or F); and R₁₀ is halogen, alkyl, cycloalkyl,         haloalkyl (e.g., trifluoromethyl), aryl (e.g., phenyl),         heteroaryl (e.g., pyridyl (for example pyrid-2-yl), or         thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl)), arylcarbonyl (e.g.,         benzoyl), alkyl sulfonyl or heteroarylcarbonyl; and     -   (iv) R₆ is H, alkyl, aryl, heteroaryl, arylalkyl [e.g., benzyl],         arylamino [e.g., phenylamino], heteroarylamino, arylalkylamino,         N,N-dialkylamino, N,N-diarylamino, or N-aryl-N-(arylalkyl)amino         [e.g. N-phenyl-N-(1,1′-biphen-4-ylmethyl)amino];         in free, salt or prodrug form.

The invention further provides the use of PDE 1 Inhibitors of Formula Ia as follows:

-   -   2.1: Formula Ia wherein R₁ is methyl;     -   2.2: Formula Ia or 2.1 wherein R₄ is H and at least one of R₂         and R₃ is lower alkyl, such that when the carbon carrying R₃ is         chiral, it has the R configuration, e.g., wherein both R₂ and R₃         are methyl, or wherein one is hydrogen and the other isopropyl;     -   2.3: Formula Ia or 2.1 wherein R₂ is H and R₃ and R₄ together         form a tri- or tetramethylene bridge, having the cis         configuration, preferably wherein the carbons carrying R₃ and R₄         have the R and S configurations respectively;     -   2.4: Formula Ia, 2.1, 2.2 or 2.3 wherein R₅ is a moiety of         formula Qa wherein R₈, R₉, R₁₁, and R₁₂ are H and R₁₀ is phenyl;     -   2.5: Formula Ia, 2.1, 2.2, or 2.3 wherein R₅ is a moiety of         formula Qa wherein R₈, R₉, R₁₁, and R₁₂ are H and R₁₀ is pyridyl         or thiadiazolyl;     -   2.6: Formula Ia, 2.1, 2.2, 2.3, 2.4, or 2.5 wherein R₅ is         attached to the 2-position nitrogen on the pyrazolo ring;     -   2.7: Formula Ia, 2.1, 2.2, 2.3, 2.4, 2.5 or 2.6 wherein R₆ is         benzyl;     -   2.8: Formula Ia, 2.1, 2.2, 2.3, 2.4, 2.5 or 2.6 wherein R₆ is         phenylamino or phenylalkylamino (e.g., benzylamino); and/or     -   2.9: Formula Ia, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, or 2.8         wherein the compounds inhibit phosphodiesterase-mediated (e.g.,         PDE1-mediated, especially PDE1B-mediated) hydrolysis of cGMP,         e.g., with an IC₅₀ of less than 1 μM, preferably less than 25 nM         in an immobilized-metal affinity particle reagent PDE assay, for         example, as described in Example 1;     -   in free or salt form.

In an another embodiment, the PDE 1 Inhibitors are compounds of Formula I wherein

-   -   (i) R₁ is methyl;     -   (ii) R₂, R₃ and R₄ are H;     -   (iii) n=1 and R_(a) and R_(b) are, independently, H or methyl;     -   (iv) R₅ is a moiety of Formula Q wherein R₈, R₉, R₁₁ and R₁₂ are         H and R₁₀ is phenyl, pyridyl (for example pyrid-2-yl), or         thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl);     -   (v) R₆ is benzyl, phenylamino or benzylamino;     -   in free or salt form.

In another embodiment, the PDE 1 Inhibitors are compounds of Formula I wherein

-   -   (i) R₁ is methyl;     -   (ii) n=0;     -   (iii) R₂ is H and R₃ and R₄ together form a tri- or         tetra-methylene bridge [pref. with the carbons carrying R₃ and         R₄ having the R and S configuration respectively]; or at least         one of R₂ and R₃ is methyl, isopropyl or arylalkoxy and R₄ is H;         or R₂ and R₃ are H and R₄ is a C₁₋₄ alkyl;     -   (iv) R₅ is a substituted heteroarylmethyl, e.g.,         para-substituted with haloalkyl; or     -   R₅ is a moiety of Formula Q wherein R₈, R₉, R₁₁ and R₁₂ are H or         halogen and R₁₀ is haloalkyl, phenyl, pyridyl (for example         pyrid-2-yl), or thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl); and     -   (v) R₆ is benzyl, phenylamino or benzylamino;     -   in free or salt form.

In another embodiment, the PDE 1 Inhibitors are compounds of Formula Ia wherein

-   -   (i) R₁ is methyl;     -   (ii) R₂ is H and R₃ and R₄ together form a tri- or         tetra-methylene bridge [pref. with the carbons carrying R₃ and         R₄ having the R and S configuration respectively]; or R₂ and R₃         are each methyl and R₄ is H; or R₂ and R₄ are H and R₃ is         isopropyl [pref. the carbon carrying R₃ having the R         configuration];     -   (iii) R₅ is a moiety of Formula Qa wherein R₈, R₉, R₁₁, and R₁₂         are H and R₁₀ is haloalkyl, phenyl, pyridyl (for example         pyrid-2-yl), or thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl); and     -   (iv) R₆ is benzyl, phenylamino or benzylamino;     -   in free or salt form.

In another embodiment, the PDE 1 Inhibitors are compounds of Formula Ia selected from the following:

For example, PDE 1 Inhibitors include compounds according to Formulae II, III and IV.

wherein

-   -   R_(a) and R_(b) are, independently, H or C₁₋₄ alkyl;     -   R₆ is phenylamino or benzylamino;     -   R₁₀ is phenyl, pyridyl (for example pyrid-2-yl), or thiadiazolyl         (e.g., 1,2,3-thiadiazol-4-yl);     -   in free or salt form.

wherein

-   -   R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene         bridge [pref. with the carbons carrying R₃ and R₄ having the R         and S configuration respectively]; or at least one of R₂ and R₃         is methyl, isopropyl or arylalkoxy and R₄ is H; or R₂ and R₃ are         H and R₄ is a C₁₋₄ alkyl;     -   R₆ is phenylamino or benzylamino;     -   R₁₀ is haloalkyl, phenyl, pyridyl (for example pyrid-2-yl), or         thiadiazolyl (e.g., 1,2,3-thiadiazol-4-yl);     -   in free or salt form.

wherein

-   -   R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene         bridge [pref. with the carbons carrying R₃ and R₄ having the R         and S configuration respectively]; or at least one of R₂ and R₃         is methyl, isopropyl or arylalkoxy and R₄ is H; or R₂ and R₃ are         H and R₄ is a C₁₋₄ alkyl;     -   R₆ is phenylamino or benzylamino;     -   R₁₀ is phenyl, pyridyl (for example pyrid-2-yl), or thiadiazolyl         (e.g., 1,2,3-thiadiazol-4-yl);     -   in free or salt form.

PDE 1 Inhibitors used in the method disclosed herein also include compounds according to Formula V:

-   -   wherein     -   R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene         bridge [pref. with the carbons carrying R₃ and R₄ having the R         and S configuration respectively]; or R₂ and R₃ are each methyl         and R₄ is H; or R₂ and R₄ are H and R₃ is isopropyl [pref. the         carbon carrying R₃ having the R configuration];     -   R₆ is phenylamino or benzylamino;     -   R₁₀ is phenyl, pyridyl, or thiadiazolyl;     -   in free or salt form.         In a preferred embodiment, the PDE 1 Inhibitors for use in the         methods of treatment described herein are a 1,3,5-substituted         6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one, of formula VI

wherein

-   -   R_(a) is methyl or C₂-C₆ alkyl;     -   R₁ is H or C₁-C₄ alkyl;

each of R₂ and R₃ is independently selected from H and C₁-C₄ alkyl, or R₂ is H or C₁-C₄ alkyl and R₃ is OH, C₂-C₄ alkanoyloxy or fluoro, or R₂ and R₃ when taken together represent C₂-C₆ alkylene, or R₂ and R₃ when taken together with the carbon atom to which they are attached represent a carbonyl group;

-   -   Ar is either (a)

wherein

-   -   each of R₄, R₅ and R₆ is independently selected from         -   H         -   C₁-C₄ alkyl,         -   C₁-C₄ alkoxy,         -   C₁-C₄ alkoxy-Z-,         -   halo,         -   halo(C₁-C₄)alkyl,         -   phenoxy, optionally substituted by up to three substitutents             each of which substitutent is independently selected from             halo, C₁₋₄ alkyl, and C₁-C₄ alkoxy,         -   nitro,         -   hydroxy,         -   hydroxy-Z-,         -   C₂-C₄ alkanoyl,         -   amino,         -   amino-Z-,         -   (C₁-C₄ alkyl)NH,         -   (C₁-C₄ alkyl)₂N—,         -   (C₁-C₄ alkyl)NH—Z—,         -   (C₁-C₄ alkyl)₂N—Z—,         -   —COOH,         -   —Z—COOH,         -   —COO(C₁-C₄ alkyl),         -   —Z—COO(C₁-C₄ alkyl)         -   C₁-C₄ alkanesulphonamido,         -   C₁-C₄ alkanesulphonamido-Z-,         -   halo(C₁-C₄)alkanesulphonamido,         -   halo(C₁-C₄)alkanesulphonamido-Z-,         -   C₁-C₄ alkanamido,         -   C₁-C₄ alkanamido-Z-,         -   HOOC—Z—NH—,         -   HOOC—Z—NH—Z—,         -   (C₁-C₄ alkyl)OOC—Z—NH—,         -   (C₁-C₄ alkyl)OOC—Z—NH—Z—,         -   C₁-C₄ alkyl-NH—SO₂—NH—,         -   C₁-C₄ alkyl-NH—SO₂—NH—Z—,         -   (C₁-C₄ alkyl)₂-N—SO₂—NH—,         -   (C₁-C₄ alkyl)₂-N—SO₂—NH—Z—,         -   C₁-C₄ alkoxy CH═CH—Z—CONH—,         -   C₁-C₄ alkoxy CH═CHCONH         -   C₁-C₄ alkyl-SO₂—N(C₁-C₄ alkyl)-,         -   C₁-C₄ alkyl-SO₂—N(C₁-C₄ alkyl)-Z-,         -   (C₁-C₄ alkyl)NH—Z—SO₂—NH—,         -   (C₁-C₄ alkyl)₂N—Z—SO₂—NH—,         -   (C₁-C₄ alkyl)NH—Z—SO₂—NH—Z—,         -   (C₁-C₄ alkyl)₂N—Z—SO₂—NH—Z—,     -   benzenesulphonamido, optionally ring substituted by up to three         substitutents each of which is independently selected from halo,         C₁₋₄ alkyl, and C₁-C₄ alkoxy,         -   C₁-C₄ alkanoyl-N(C₁-C₄ alkyl)-,         -   C₁-C₄ alkanoyl-N(C₁-C₄ alkyl)-Z-,         -   C₁-C₄ alkoxycarbonyl-CH(CH₂OH)NHSO₂—,         -   —SO₃H,         -   —SO₂NH₂,         -   H₂NOC—CH(CH₂OH)—NHSO₂—,         -   HOOC—Z—O—, and         -   (C₁-C₄ alkyl)OOC—Z—O—,     -   or optionally one of R₄, R₅ and R₆ is a G-Het group and wherein         the others of R₄, R₅ and R₆ are independently selected from the         R₄, R₅ and R₆ substitutents listed above;     -   Z is C₁-C₄ alkylene,     -   G is a direct link, Z, O, —SO₂NH—, SO₂, or —Z—N(C₁-C₄         alkyl)SO₂—,     -   Het is a 5- or 6-membered heterocyclic group containing 1, 2, 3         or 4 nitrogen heteroatoms; or 1 or 2 nitrogen heteroatoms and 1         sulphur heteroatom or 1 oxygen heteroatom; or the heterocyclic         group is furanyl or thiophenyl; wherein the Het group is         saturated or partially or fully unsaturated and optionally         substituted by up to 3 substitutents, wherein each substitutent         is independently selected from C₁-C₄ alkyl, oxo, hydroxy, halo,         and halo(C₁-C₄) alkyl;     -   or (b) any one of the following bicyclic groups:         -   benzodioxolanyl,         -   benzodioxanyl,         -   benzimidazolyl,         -   quinolinyl,         -   indolyl,         -   quinazolinyl,         -   isoquinolinyl,         -   benzotriazolyl,         -   benzofuranyl,         -   benzothiophenyl,         -   quinoxalinyl, or         -   phthalazinyl,     -   wherein said bicyclic Ar groups are linked to the neighbouring         —C(R₂R₃)— group via the benzo ring portion,     -   and wherein the heterocyclic portion of said bicyclic Ar group         is optionally partially or fully saturated, said group being         optionally substituted by one or more of C₁-C₄ alkyl, halo,         hydroxy, oxo, amino, and C₁-C₄ alkoxy;

or a pharmaceutically acceptable salt of the compound, or a pharmaceutically acceptable solvate of the compound or the salt.

For example, PDE 1 Inhibitors for use in the present invention include 1,3,5,-substituted, 6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one, in free or pharmaceutically acceptable salt form, particularly compounds of Formula VI or the following formulae:

-   -   3.2 Of Formula VI wherein R_(a) is a C₂₋₅ alkyl group;     -   3.3 Of Formula VI wherein R_(a) is a C₂₋₄ alkyl group;     -   3.4 Of Formula VI wherein R_(a) is a C₃ alkyl group;     -   3.5 Of Formula VI wherein R_(a) is methyl;     -   3.6 Of Formula VI, 3.2, 3.3, 3.4 or 3.5 wherein R₁ is a C₁₋₆         alkyl group;     -   3.7 Of any of the preceding formulae wherein R₁ is a C₁₋₃ alkyl         group;     -   3.8 Of any of the preceding formulae wherein R₁ is a methyl         group;     -   3.9 Of any of the preceding formulae wherein R₂ is H,     -   3.10 Of any of the preceding formulae wherein R₃ is H,     -   3.11 Of any of the preceding formulae wherein R₄, R₅ and R₆ are         independently selected from H, (C₁₋₄ alkyl)₂N—, C₁₋₄         alkanesulphonamido and benzenesulphonamido;     -   3.12 Of any of the preceding formulae wherein R₄, R₅ and R₆ are         independently selected from H, diethylamino, methanesulphonamido         and benzenesulphonamido;     -   3.13 Of any of the preceding formulae wherein Ar is         4-diethylaminophenyl;     -   3.14 Of any of the preceding formulae wherein Ar is         2-methanesulphonamidophenyl;     -   3.15 Of any of the preceding formulae wherein Ar is         4-benzenesulphonamidophenyl;     -   3.16 Of any of the preceding formulae wherein one of R₄, R₅ and         R₆ is (C₁₋₄ alkyl)₂N— and wherein the other two of R₄, R₅ and R₆         are H.     -   3.17 Of any of the preceding formulae wherein one of R₄, R₅ and         R₆ is diethylamino and wherein the other two of R₄, R₅ and R₆         are H.     -   3.18 Of any of the preceding formulae wherein R_(a) is methyl;     -   3.19 Of any of the preceding formulae wherein R_(a) is C₂-C₆         alkyl;     -   3.20 Of any of the preceding formulae wherein the compound is         selected from the following:

-   -   3.21 Of any of the preceding formulae wherein the compound is

-   -   in free or salt form;     -   3.22 A compound which is a 1,3,5,-substituted,         6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-7-one, in free or         pharmaceutically acceptable salt form, e.g. a compound of         Formula VI or according to any of formulae 3.2-3.21, wherein the         compound inhibits phosphodiesterase-mediated (e.g.,         PDE1-mediated, especially PDE1B-mediated) hydrolysis of cGMP,         e.g., with an IC₅₀ of less than 1 μM, preferably less than 25 nM         in an immobilized-metal affinity particle reagent PDE assay, for         example, as described in Example 1 below.

In another embodiment, the PDE 1 Inhibitors for use in the methods of treatment described herein are substituted (imidazo, pryimido or diazepino)[2,1-b]purin-4-ones of Formula VIIa or VIIb:

in free, salt or prodrug form, including its enantiomers, diasterisomers and racemates, wherein:

-   -   i) q=0, 1 or 2;     -   ii) R¹, R^(a), R^(b), R^(c) and R^(d) are each independently H,         alkyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl groups,         -   wherein each alkyl group of R¹, R^(a), R^(b), R^(c) and             R^(d) is independently unsubstituted or substituted with 1             to 5 independently selected R³ moieties which can be the             same or different, each R³ moiety being independently             selected from the group consisting of hydroxy, alkoxy,             cycloalkoxy, aryloxy, alkylthio, arylthio, aryl, haloaryl,             heteroaryl, cycloalkyl, heterocycloalkyl, amino, alkylamino,             dialkylamino, cycloalkylamino and heterocycloalkylamino             groups;         -   wherein each of the aryl, heteroaryl, cycloalkyl and             heterocycloalkyl groups of R¹, R^(a), R^(b), R^(c) and R^(d)             is independently unsubstituted or substituted with 1 to 5             independently selected R⁴ moieties which can be the same or             different, each R⁴ moiety being independently selected from             the group consisting of: halo, optionally substituted aryl             (e.g., phenyl, chlorophenyl, methoxyphenyl), heteroaryl             (e.g., pyridyl, pyrrolyl), nitro, cyano, haloalkyl,             haloalkoxy, alkyl, alkoxy, cycloalkyl, heterocycloalkyl             (e.g., pyrrolidinyl, morpholin-4-yl, pyrrol-1-yl),             cycloalkylalkyl, amino, alkylamino, dialkylamino, —OCF₃,             acyloxy, —OR⁸, —C(O)R⁹, —C(O)OR⁸, —NR¹⁰C(O)R⁹, —NR¹⁰C(O)OR⁸,             —NR¹⁰S(O)₂R⁹, —S(O)₀₋₂R⁹ groups, carbonyl when two hydrogens             attached to the same carbon atom of the cycloalkyl or             heterocycloalkyl group of R′ are substituted, and ═CR⁸R⁹             when two hydrogens attached to the same carbon atom of the             cycloalkyl or heterocycloalkyl groups of R¹ are substituted,         -   wherein each of the aryl, heteroaryl, cycloalkyl and             heterocycloalkyl groups of the R³ and R⁴ moieties above is             independently unsubstituted or substituted with 1 to 5             independently selected R¹² moieties which can be the same or             different, each R¹² moiety being independently selected from             the group consisting of: halo, phenyl, nitro, cyano,             haloalkyl, haloalkoxy, alkyl, cycloalkyl, cycloalkylalkyl,             amino, alkylamino, —OCF₃, acyloxy, —OR⁸, —C(O)R⁹, —C(O)OR⁸,             —NR¹⁰C(O)R⁹, —NR¹⁰C(O)OR⁸, —NR¹⁰S(O)₂R⁹, —S(O)₀₋₂R⁹ groups,             carbonyl when two hydrogens attached to the same carbon atom             of the cycloalkyl or heterocycloalkyl group of R³ or R⁴ are             substituted, and ═CR⁸R⁹ when two hydrogens attached to the             same carbon atom of the cycloalkyl or heterocycloalkyl group             of R³ or R⁴ are substituted; or     -   iii) R^(a) and R^(b), together with the carbon to which they are         both attached, form a 4- to 7-membered cycloalkyl or         heterocycloalkyl ring, and R^(c) and R^(d) are each         independently H or an alkyl group; or     -   iv) R^(a) and R^(c), together with the respective carbons to         which they are attached, form a 4- to 7-membered cycloalkyl or         heterocycloalkyl ring, and R^(b) and R^(d) are each         independently H or an alkyl group, preferably R^(a) and R^(c)         together have the cis configuration, e.g., where the carbons         carrying R^(a) and R^(c) have the R and S configurations,         respectively;     -   v) R² is H, halo, alkyl, haloalkyl, alkoxy, alkylthio, amino,         aminosulfonyl, monoalkylamino, dialkylamino, hydroxyalkylamino,         aminoalkylamino, carboxy, alkoxycarbonyl, aminocarbonyl or         alkylaminocarbonyl group,         -   wherein each alkyl group of R² is independently             unsubstituted or substituted with 1 to 5 independently             selected R¹³ moieties which can be the same or different,             each R¹³ moiety being independently selected from the group             consisting of halo, hydroxy, alkoxy, alkyl, aryl (e.g.,             phenyl, naphthyl) heteroaryl (e.g., 1H-imidazol-2-yl),             cycloalkyl, heterocycloalkyl (e.g., pyrrolidin-1-yl), amino,             monoalkylamino or dialkylamino group,         -   wherein each aryl group of R¹³ is independently             unsubstituted or substituted with 1 to 5 independently             selected R⁴ moieties which can be the same or different;     -   vi) Y is H or an alkyl group substituted with (i) an aryl,         heteroaryl, cycloalkyl, hydroxy, alkoxy, amino, monoalkylamino         or dialkylamino group, or (ii) an aryl group substituted with         from one to three moieties each independently selected from the         group consisting of: halo, alkyl, phenyl, hydroxy, alkoxy,         phenoxy, amino, monoalkylamino and dialkylamino group;     -   vii) each R⁸ is independently H, alkyl or aryl;     -   viii) each R⁹ is independently H, alkyl, aryl or —NR¹⁰R¹¹;     -   ix) each R¹⁰ is independently H, alkyl, aryl, heteroaryl,         arylalkyl or heteroarylalkyl, wherein each alkyl, aryl,         heteroaryl, arylalkyl or heteroarylalkyl of R¹⁰ is unsubstituted         or independently substituted with 1 to 5 R¹⁴ moieties which can         be the same or different, each R¹⁴ moiety being independently         selected from the group consisting of: halo, alkyl, aryl,         cycloalkyl, —CF₃, —OCF₃, —CN, —OR⁸, —CH₂OR⁸, —C(O)OR⁸ and         —C(O)NR⁸R⁸; and     -   x) each R¹¹ is independently H, alkyl, aryl, heteroaryl,         arylalkyl or heteroarylalkyl, wherein each alkyl, aryl,         heteroaryl, arylalkyl or heteroarylalkyl of R¹¹ is unsubstituted         or independently substituted with 1 to 5 R¹⁴ moieties which can         be the same or different.

The invention further provides the use of PDE 1 Inhibitors of Formula VIIa or VIIb, in free or salt form, as follows:

-   -   4.1: Formula VIIa or VIIb, wherein q=0, 1 or 2;     -   4.2: Formula VIIa or VIIb, wherein q=0;     -   4.3: Formula VIIa or VIIb or 4.1 or 4.2, wherein R₁ is alkyl;     -   4.4: Formula VIIa or VIIb or 4.1-4.3, wherein R¹ is methyl;     -   4.5: Formula VIIa or VIIb or 4.1-4.4, wherein R^(a) and R^(c),         together with the respective carbons to which they are attached,         form a 4- to 7-membered cycloalkyl or heterocycloalkyl ring, and         R^(b) and R^(d) are each independently H or an alkyl group;     -   4.6: Formula VIIa or VIIb or 4.1-4.4, wherein R^(a) and R^(c),         together with the respective carbons to which they are attached,         form a 5-membered heterocycloalkyl ring, and R^(b) and R^(d) are         each independently H,     -   4.7: Formula 4.6 wherein R^(a) and R^(c) together have a cis         configuration;     -   4.8: Formula VIIa or VIIb or 4.1-4.4, wherein R^(a) and R^(b),         together with the respective carbons to which they are attached,         form a 5-membered heterocycloalkyl ring, and R^(c) and R^(d) are         each independently H,     -   4.9: Formula VIIa or VIIb or 4.1-4.7, wherein R² is alkyl or         haloalkyl;     -   4.10: Formula VIIa or VIIb or 4.1-4.7, wherein R² is         biphenyl-4-ylmethyl;     -   4.11: Formula VIIa or VIIb or 4.1-4.7, wherein R² is benzyl;     -   4.12: Formula VIIa or VIIb or 4.1-4.7, wherein R² is         cyclopentylmethyl;     -   4.13: Formula VIIa or VIIb or 4.1-4.7, wherein R² is         cyclopropylmethyl; and/or     -   4.14: Formula VIIa or VIIb or 4.1-4.12, wherein Y is benzyl;     -   4.15: Of any of the preceding formulae wherein the compound is         selected from the following:

-   -   4.16: Of any of the preceding formulae wherein the compound is

-   -   in free or salt form;     -   4.17: A compound which is a substituted         imidazo[2,1-b]purin-4-one, in free or pharmaceutically         acceptable salt form, e.g. a compound of Formula VIIa or         according to any of formulae 4.1-4.16, wherein the compound         inhibits phosphodiesterase-mediated (e.g., PDE1-mediated,         especially PDE1B-mediated) hydrolysis of cGMP, e.g., with an         IC₅₀ of less than 1 μM, preferably less than 25 nM in an         immobilized-metal affinity particle reagent PDE assay, for         example, as described in Example 1 below.

Preferably, compounds of Formula VIIa or VIIb are selected from a group consisting of (6aR,9aS)-5,6a,7,8,9,9a-hexahydro-5-methyl-2,3-bis(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one, (6aR,9aS)-2-(biphenyl-4-ylmethyl)-5,6a,7,8,9,9a-hexahydro-5-methyl-3-(phenylmethyl)cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one, 5′-methyl-2′,3′-bis(phenylmethyl)spiro[cyclopentane-1,7′(8′H)-[3H]imidazo[2,1-b]purin]-4′(5′H)-one and 5′-methyl-2′-(biphenyl-4-ylmethyl)-3′-(phenylmethyl)spiro-[cyclopentane-1,7′(8′H)-[3H]imidazo[2,1-b]purin]-4′(5′H)-one, in free or pharmaceutically acceptable salt form.

In an especially preferred embodiment, compound of Formula VIIa is (6aR,9aS)-2-(biphenyl-4-ylmethyl)-5,6a,7,8,9,9a-hexahydro-5-methyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one, in free or salt form.

The numbering of substituted imidazo[2,1-b]purin-4-one of Formula VIIa or VIIb as described herein is shown below as an example, wherein q=0:

wherein q=1:

In another embodiment, the PDE 1 Inhibitors for use in the methods of treatment described herein are Compounds of Formula VIIIa or VIIIb:

in free or salt form, wherein:

-   -   J is oxygen or sulfur,     -   R¹ is hydrogen, alkyl or alkyl substituted with aryl or hydroxy;     -   R² is hydrogen, aryl, heteroaryl, cycloalkyl, alkyl or alkyl         substituted with aryl, heteroaryl, hydroxy, alkoxy, amino,         monoalkyl amino or dialkylamino, or —(CH₂)_(m)TCOR²⁰ wherein m         is an integer from 1 to 6, T is oxygen or —NH— and R²⁰ is         hydrogen, aryl, heteroaryl, alkyl or alkyl substituted with aryl         or heteroaryl;     -   R³ is hydrogen, halo, trifluoromethyl, alkoxy, alkylthio, alkyl,         cycloalkyl, aryl, aminosulfonyl, amino, monoalkylamino,         dialkylamino, hydroxyalkylamino, aminoalkylamino, carboxy,         alkoxycarbonyl or aminocarbonyl or alkyl substituted with aryl,         hydroxy, alkoxy, amino, monoalkylamino or dialkylamino;     -   R^(a), R^(b), R^(c) and R^(d) independently represent hydrogen,         alkyl, cycloalkyl or aryl; or (R^(a) and R^(b)) or (R^(c) and         R^(d)) or (R^(b) and R^(c)) can complete a saturated ring of 5-         to 7-carbon atoms, or (R^(a) and R^(b)) taken together and         (R^(b) and R^(c)) taken together, each complete a saturated ring         of 5- to 7-carbon atoms, wherein each ring optionally can         contain a sulfur or oxygen atom and whose carbon atoms may be         optionally substituted with one or more or the following:         alkenyl, alkynyl, hydroxy, carboxy, alkoxycarbonyl, alkyl or         alkyl substituted with hydroxy, carboxy or alkoxycarbonyl; or         such saturated ring can have two adjacent carbon atoms which are         shared with an adjoining aryl ring; and     -   n is zero or one.

The invention further provides the use of PDE 1 Inhibitors of Formula VIIIa or VIIIb as follows:

-   -   5.1: Formula VIIIa or VIIIb, wherein J=O     -   5.2: Formula VIIIa or VIIIb or 5.1, wherein R¹ is alkyl.     -   5.3: Formula VIIIa or VIIIb, 5.1 or 5.2, wherein R² is hydrogen,         benzyl, 4-chlorobenzyl, cyclohexylmethyl or         trimethylacetoxymethyl.     -   5.4: Formula VIIIa or VIIIb, 5.1, 5.2 or 5.3, wherein R³ is         hydrogen, or alkyl such as methyl or ethyl.     -   5.5: Formula VIIIa or VIIIb, 5.1, 5.2, 5.3 or 5.4, wherein n is         zero; and     -   5.6: Formula VIIIa or VIIIb, 5.1, 5.2, 5.3, 5.4 or 5.5, wherein         R^(a) and R^(b) form a saturated 5 membered ring, or (R^(b) and         R^(c)) form a saturated 5, 6 or 7 membered ring, or (R^(a) and         R^(b)) and (R^(b) and R^(c)) each complete a saturated ring and         each ring contains 5 or 6 carbon atoms.     -   5.7 Formula VIIIa or VIIIb, in free or salt form, selected from         the following:

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(phenylmethyl)cyclopenta[4,5]imidazo-[2,1-b]purin-4-one;

-   7,8-Dihydro-5-methyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   5,7,8,9-Tetrahydro-5-methyl-3-(phenylmethyl)pyrimido[2,1-b]purin-4(3H)-one;

-   7,8-Dihydro-8-phenyl-5-methyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   5′,7′-Dihydro-5′-methyl-3′-(phenylmethyl)spiro[cyclohexane-1,8′-(8H)imidazo-[2,1-b]purin]-4′(3′H)-one;

-   cis-5,6a,11,11a-Tetrahydro-5-methyl-3-(phenylmethyl)indeno[1′,2′:4,5]imidazo-[2,1-b]purin-4(3H)-one;

-   5′,7′-Dihydro-2′,5′dimethyl-3′-(phenylmethyl)spiro{cyclohexane-1,7′(8′H)-imidazo[2,1-b]purin}-4′-(3′H)-one;

-   7,8-Dihydro-2,5,7,7,8(R,S)-pentamethyl-3H-imidazo[2,1-b]purin-4(5H)-one;

-   cis-5,6a,7,11b-Tetrahydro-5-methyl-3-(phenylmethyl)indeno[2′,1′,:4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4-(3H)-one;

-   5′-Methyl-3′-(phenylmethyl)-spiro[cyclopentane-1,7′-(8′H)-(3′H)imidazo[2,1-b]purin]-4-(5′H)-one;

-   7,8-Dihydro-2,5,7,7-tetramethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5′H)-one;

-   7,8-Dihydro-7(R)-phenyl-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-3,7(R)-bis(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   (±)-7,8-Dihydro-2,5-dimethyl-7-ethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   6a(S)-7,8,9,10,10a(R)-Hexhydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   6a(R)-7,8,9,10,10a(S)-hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo-[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(R)-isopropyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5,7(R)-trimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   cis-7,7a,8,9,10,10a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-cyclopenta-[5,6]pyrimido[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylpropyl)-3-(phenylmethyl)-3H-imidazo-[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(R)-(2-methylpropyl)-3-(phenylmethyl)-3H-imidazo-[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(R,S)-(methoxycarbonyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(R,S)-(1-propyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylethyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5,7,7,8(R,S)-pentamethyl-3H-imidazo[2,1-b]purin-4(5H)-one;

-   5,7,8,9-Tetrahydro-2,5,7,9(R,S)-pentamethyl-3-(phenylmethyl)-pyrimido[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(S),7,8,9,9a(R)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-6a,7,8,9,10,10a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   5′,7′-Dihydro-2′,5′-dimethyl-3′-(phenylmethyl)spiro[cyclohexane-1,8-(8H)-imidazo[2,1-b]purin]-4-(3′H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclohept-[6,7]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4-(5H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-phenyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-2-phenyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methylcyclopenta[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethylcyclopenta[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a(R),     7,8,9,9a(S)-Hexahydro-2,5-di-methylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   2′,5′-dimethyl-spiro{cyclopentane-1,7′-(8′H)-(3′H)-imidazo[2,1-b]purin}-4′(5′H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(R)-(1-methylethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5,7,7-tetramethyl-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   6a(R),7,8,9,10,10a(S)-Hexahydro-2,5-dimethyl-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   5′,7′-Dihydro-2′,5′-dimethylspiro{cyclohexane-1,7-(8′H)-imidazo[2,1-b]purin}-4′(3′H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(phenylmethyl)cyclopenta[4,5]-imidazo[2,1-b]purin-4(3H)-thione;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-thione;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(4-chlorophenylmethyl)cyclopenta[4,5]-imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(cyclohexylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(2-naphthylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-bromophenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R)-7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-methoxyphenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2,3,5-trimethylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2-(hydroxymethyl)-5-methyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2-methylthio-5-methyl-3-(Phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-3,4,5,6a,7,8,9,9a-Octahydro-5-methyl-4-oxo-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-2-carboxylic     acid;

-   cis-3,4,5,6a,7,8,9,9a-Octahydro-5-methyl-4-oxo-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-2-carboxylic     acid, methyl ester;

-   cis-5,6a,7,8,9,9a-Hexahydro-2-bromo-5-methyl-3-(phenylmethyl)cyclopent[4,5]imidazo[2,1-b]purin-4(3H)one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2-(methylaminosulfonyl)-5-methyl-3-(phenylmethyl)cyclopent[4,5]imidazo[2,1-b]purin-4(3H)one;

-   cis-1-Cyclopentyl-5,6a,7,8,9,9a-hexahydro-5-methylcyclopent[4,5]imidazo[2,1-b]purin-4-(1H)one;

-   cis-5,6a,7,8,9,9a-Hexahydro-3,5-bis-(phenylmethyl)cyclopent(4,5)imidazo[2,1-b]purin-4(3H)one;

-   cis-6a,7,8,9,10,10a-Hexahydro-3,5-bis-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)one;

-   cis-3-Cyclopentyl-5,6a,7,8,9,9a-hexahydro-5-methylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)one;

-   5′-Methyl-3′-(phenylmethyl)spiro[cyclopentane-1,7-(8′H)-(3′H)imidazo[2,1-b]purin]-4-(5H)one;

-   2′,5′-Dimethyl-3′-(phenylmethyl)-spiro[cyclopentane-1,7-(8′H)-(3H)imidazo[2,1-b]purin]-4-(5′H)one;

-   cis-5,6a,(R)7,8,9,9a(S)-Hexahydro-5-methyl-3-(phenylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)one;

-   cis-3-Cyclopentyl-5,6a,7,8,9,9a-Hexahydro-2,5-dimethylcyclopent[4,5]imidazo-[2,1-b]purin-4(3H)one;

-   5′-Methyl-2′-trifluoromethyl-3′-(phenylmethyl)spiro{cyclo-pentane-1,7′(8′H)-(3′H)imidazo[2,1-b]purin}-4-(5′H)-one;

-   7,8-Dihydro-5,7,7-trimethyl-2-trifluoromethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one;

-   (+/−)-cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-trifluoromethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   (+/−)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-(phenylmethyl)-3H-pentaleno[6a′,1′:4,5]imidazo[2,1-b]purin-4(5H)-one;

-   (+)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-phenylmethyl-3H-pentaleno[6a′,1′:4,5]imidazo[2,1-b]purin-4(5H)-one;

-   (−)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-phenylmethyl-3H-pentaleno[6a′,1′:4,5]Imidazo[2,1-b]purin-4(5H)-one;

-   (+/−)     6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one;

-   (+)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one;

-   (−)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one;

-   6a,7,8,9,10,10a,11,12,13,13a-Decahydro-2,5-dimethyl-(3-phenylmethyl)-napth[1,8a-d]imidazo[2,1-b]purin-4(5H)one;

-   7(R)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(3H)-one;

-   7(R)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3H-imidazo[2,1-b]purin-4(5H)-one;

-   7(S)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(3H)-one;

-   7(S)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3H-imidazo[2,1-b]purin-4(5H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-[3-(trimethylacetoxy)methyl]-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-pyridylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-[2-(4-morpholinyl)-ethyl]cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-[acetoxymethyl]cyclopent-[4,5]imidazo[2.1-b]purin-4(3H)-one;

-   5,6a,7,8,9,9a-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(R),7,8,9,9a(S)-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   5,6a(S),7,8,9,9a(R)-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;

-   cis-6a,7,8,9,10,10a-Hexahydro-2,5,7-trimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one;

-   cis-5,6a,7,8,9,9a-Hexahydro-2,5,6a-trimethylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one;     or

-   cis-[6a,7,8,9,10,10a-Hexahydro-2,5,7-trimethyl-3H-benzimidazo[2,1-b]purin-4(5H)-one],     -   in free or salt form.     -   5.8: A compound which is a substituted         imidazo[2,1-b]purin-4-one, in free or pharmaceutically         acceptable salt form, e.g. a compound of Formula VIIIa, VIIIb or         according to any of formulae 5.1-5.7, wherein the compound         inhibits phosphodiesterase-mediated (e.g., PDE 1-mediated,         especially PDE 1 B-mediated) hydrolysis of cGMP, e.g., with an         IC₅₀ of less than 10 μM, preferably less than 100 nM in an         immobilized-metal affinity particle reagent PDE assay, for         example, as described in Example 1 below.

In another embodiment, the PDE 1 Inhibitors for use in the methods of treatment described herein are Compounds of Formula IXa or IXb

or a pharmaceutically acceptable salt thereof, wherein, q=0 or 1; R¹ is H, cycloalkyl, alkyl, R²³-alkyl- or R²⁶; R^(a), R^(b) and R^(c) are, independently of one another, each H, alkyl, cycloalkyl, aryl, R²²-aryl- or R²⁴-alkyl-; or R^(a) and R^(b), together with the carbon to which they are both attached, form a 4- to 7-membered ring, and R^(c) is H or alkyl; or R^(a) and R^(c), together with the respective carbons to which they are attached, form a 4- to 7-membered ring, and R^(b) is H or alkyl;

-   -   (i) X is a bond;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is monohaloalkyl, polyhaloalkyl, provided that it is not             trifluoromethyl, azido, cyano, oximino, cycloalkenyl,             heteroaryl, R²²-heteroaryl- or R²⁷-alkyl-;     -   (ii) X is a bond;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is H, halo, —CONHR⁶, —CONR⁶R⁷, —CO₂R⁶, monohaloalkyl,             polyhaloalkyl, azido, cyano, —C═N—OR⁶, cycloalkyl,             cycloalkylalkyl, R²⁶, aminosulfonyl, alkyl or R²³-alkyl-     -   (iii) X is —O— or —S—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is R²⁶, cycloalkyl cycloalkylalkyl, heterocycloalkyl,             cycloalkenyl or R²⁶-alkyl-;     -   (iv) X is —O— or —S—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl,             heterocycloalkyl, cycloalkenyl or R²⁸-alkyl-;     -   (v) X is —SO— or —SO₂—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl,             heterocycloalkyl, cycloalkenyl or R²⁸-alkyl-;     -   (vi) X is —NR⁸—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is (R²⁹)_(p)-alkyl-, cycloalkyl, (R³⁰)_(p)-cycloalkyl-,             cycloalkenyl, (R³⁰)_(p)-cycloalkenyl-, heterocycloalkyl or             (R³⁰)_(p)-heterocycloalkyl-:     -   (vii) X is —NR⁸—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl,             heterocycloalkyl, cycloalkenyl or R³¹-alkyl-; or     -   (viii) X is —C≡C—;         -   Y is aryl-alkyl or R²²-aryl-alkyl-; and         -   R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl or R²³-alkyl-;             where,     -   R⁶ is H or R⁷;     -   R⁷ is alkyl, cycloalkyl or cycloalkylalkyl;     -   R⁸ is heterocycloalkyl or R⁶;     -   R²¹ is 1-6 substituents each independently selected from the         group consisting of halo, hydroxy, alkoxy, phenoxy, phenyl,         nitro, aminosulfonyl, cyano, monohaloalkyl, polyhaloalkyl,         thiol, alkylthio, cycloalkyl, cycloalkylalkyl, amino,         alkylamino, acylamino, carboxyl, —C(O)OR³⁴, carboxamido, —OCF₃         and acyloxy;     -   R²² is 1-6 substituents each independently selected from the         group consisting of alkyl and R²¹;     -   R²³ is cycloalkoxy aryloxy, alkylthio, arylthio, cycloalkyl or         R²⁸;     -   R²⁴ is cycloalkyl or R²⁶;     -   R²⁵ is hydroxy, alkoxy, amino, monoalkylamino, dialkylamino or         R²⁶;     -   R²⁶ is aryl, R²²-aryl-, heteroaryl or R²²-heteroaryl-;     -   R²⁷ is cycloalkoxy, aryloxy, alkylthio, arylthio, heteroaryl,         R²²-heteroaryl-, cycloalkyl, heterocycloalkyl, cycloalkenyl,         cycloalkylamino or heterocycloalkylamino;     -   R²⁸ is cycloalkylamino, heterocycloalkylamino or R²⁵;     -   R²⁹ is alkoxy, cycloalkylamino, heterocycloalkylamino or R²⁶;     -   R³⁰ is halo, hydroxy, alkoxy, amino, aminosulfonyl, cyano,         monohaloalkyl, polyhaloalkyl, thiol, alkylthio, alkyl,         cycloalkyl, cycloalkylalkyl or acyloxy;     -   R³¹ is cycloalkyl or R²⁸;     -   R³⁴ is alkyl, aryl, aralkyl and heteroaryl; and     -   p is 1 to 4.

The invention further provides the use of PDE 1 Inhibitors of Formula IXa or IXb as follows:

-   -   6.1 Formula IXa or IXb selected from a group consisting of:

-   -   6.2 Formula IXa or IXb, in free or salt form, selected from a         group consisting of:

in free or salt form.

In another embodiment, the invention provides the use of PDE 1 Inhibitors of Formula X:

in free or a pharmaceutically acceptable salt thereof, wherein: R₁, R₂ and R₃ are independently selected from the group consisting of hydrogen, lower alkyl, lower alkoxy, halogeno, hydroxy, (di-lower alkyl)amino, 4-morpholinyl, 1-pyrrolidinyl, 1-pyrrolyl, —CF₃, —OCF₃, phenyl and methoxyphenyl; or R₁ and R₂ together are methylenedioxy; or R₁ and R₂ together with the carbon atoms to which they are attached form a benzene ring; and R^(a) is hydrogen and R^(b) and R^(c), together with the carbon atoms to which they are attached, form a saturated ring of 5 carbons; or R^(a) is lower alkyl, R^(b) is hydrogen or lower alkyl, and R^(c) is hydrogen; or R^(a), R^(b) and the carbon atom to which they are attached form a saturated ring of 5-7 carbons, and R^(c) is hydrogen; or R^(a) is hydrogen, and R^(b), R^(c) and the carbon atoms to which they are attached form a tetrahydrofuran ring; or R^(a) and R^(b), together with the carbon atom to which they are attached, and R^(b) and R^(c), together with the carbon atoms to which they are attached, each form a saturated ring of 5-7 carbons.

In a further embodiment, the invention provides the use of PDE 1 Inhibitors of Formula X as follows:

-   -   7.1 Formula X, wherein R₁, R₂ and R₃ are independently selected         from the group consisting of hydrogen, lower alkyl, lower         alkoxy, halogeno, hydroxy, (di-lower alkyl)amino, 4-morpholinyl,         1-pyrrolidinyl, 1-pyrrolyl, —CF₃, —OCF₃, phenyl and         methoxyphenyl; or R₁ and R₂ together are methylenedioxy; or R₁         and R₂ together with the carbon atoms to which they are attached         form a benzene ring;     -   7.2 Formula X or 7.1, wherein R₁ is H, methoxy or         trifluoromethyl;     -   7.3 Formula X or 7.1 or 7.2, wherein R₁ is H,     -   7.4 Formula X or any of 7.1-7.3, wherein R₂ is selected from a         group consisting of H, halo (e.g., F, Cl), methoxy, methyl,         trifluoromethyl, dimethylamino, phenyl, methoxyphenyl-, —OCF₃,         3,4-OCH₂O—, pyrrolidin-1-yl, pyrol-1-yl and morpholin-4-yl;     -   7.5 Formula X or any of 7.1-7.4, wherein R₁ and R₂ together with         the carbon atoms to which they are attached form a benzene ring;     -   7.6 Formula X or any of 7.1-7.5, wherein R₃ is H or methoxy;     -   7.7 Formula X or any of 7.1-7.6, wherein R₃ is H;     -   7.8 Formula X or any of 7.1-7.7, wherein R^(a) is hydrogen and         R^(b) and R^(c), together with the carbon atoms to which they         are attached, form a saturated ring of 5 carbons; or R^(a) is         lower alkyl, R^(b) is hydrogen or lower alkyl, and R^(c) is         hydrogen; or R^(a), R^(b) and the carbon atom to which they are         attached form a saturated ring of 5-7 carbons, and R^(c) is         hydrogen; or R^(a) is hydrogen, and R^(b), R^(c) and the carbon         atoms to which they are attached form a tetrahydrofuran ring; or         R^(a) and R^(b), together with the carbon atom to which they are         attached, and R^(b) and R^(c), together with the carbon atoms to         which they are attached, each form a saturated ring of 5-7         carbons;     -   7.9 Formula X or any of 7.1-7.8, wherein R^(a) is hydrogen and         R^(b) and R^(c) together with the carbon atoms to which they are         attached, form a saturated ring of 5 carbons, and wherein R₁, R₂         and R₃ are as defined in the following table

R₁ R₂ R₃ H H H —OCH₃ H H H F H H —OCH₃ H H OH H H —CH₃ H H (CH₃)₂N— H —OCH₃ —OCH₃ —OCH₃ —OCH₃ —OCH₃ H —CF₃ H H H C₆H₅— H H —OCF₃ H H

H H

H 3,4-OCH₂O— H H

H H

H R₁ and R₂, together with the H carbon atoms to which they are attached form a benzene ring H Cl H.

-   -   7.10 Formula X or any of 7.1-7.9, selected from a group         consisting of

-   -   7.11 Formula X or any of 7.1-7.9, selected from a group         consisting of:

-   2′-benzyl-5′-methyl-spiro[cyclopentane-1′,7′(8′H)-[3′H]-imidazo[2,1-b]purin]-4′-(5′H)-one;

-   2′-benzyl-5,7,7-trimethyl-3H-imidazo[2,1-b]purin-4-(5H)-one;

-   (+)-2-benzyl-7,8-dihydro-5-methyl-7-(1-methylethyl)-1H-imidazo[2,1-b]-purin-4(5H)-one;

-   (+,−)-6a,7,8,9,9a,10,11,11a-octahydro-5-methyl-2-(3,4-methylene-dioxyphenylmethyl)-3H-pentalen[6a,1:4,5]imidazo[2,1-b]purin-4(5H)-one;     and

-   (+)-cis-6a,7,9,9a-tetrahydro-5-methyl-2-[4-(trifluoromethyl)-phenylmethyl]-3H-furo[3′,4′:4,5]imidazo[2,1-b]purin-4(5H)-one,     -   in free or salt form.     -   7.12 Formulae X or 7.1-7.11, wherein the compounds inhibit         phosphodiesterase-mediated (e.g., PDE1-mediated, especially         PDE1B-mediated) hydrolysis of cGMP, e.g., with an IC₅₀ of less         than 1 μM, preferably less than 25 nM in an immobilized-metal         affinity particle reagent PDE assay, for example, as described         in Example 1;

In another embodiment, the invention provides the use of PDE 1 Inhibitors selected from the following:

in free or salt form (Formula XI).

If not otherwise specified or clear from context, the following terms as used herein have the following meanings:

-   -   a. “Alkyl” as used herein is a saturated or unsaturated         hydrocarbon moiety, preferably saturated, preferably one to         seven carbon atoms in length, which may be linear or branched,         and may be optionally substituted, e.g., mono-, di-, or         tri-substituted, e.g., with halogen (e.g., chloro or fluoro),         hydroxy, or carboxy.     -   b. “Cycloalkyl” as used herein is a saturated or unsaturated         nonaromatic hydrocarbon moiety, preferably saturated, preferably         comprising three to nine carbon atoms, at least some of which         form a nonaromatic mono- or bicyclic, or bridged cyclic         structure, and which may be optionally substituted, e.g., with         halogen (e.g., chloro or fluoro), hydroxy, or carboxy.     -   c. “Heterocycloalkyl” as used herein is a saturated or         unsaturated nonaromatic hydrocarbon moiety, preferably         saturated, preferably comprising three to nine carbon atoms, at         least one atom selected from a group consisting of N, O or S, at         least some of which form a nonaromatic mono- or bicyclic, or         bridged cyclic structure, and which may be optionally         substituted, e.g., with halogen (e.g., chloro or fluoro),         hydroxy, or carboxy. Examples of heterocycloalkyl include         pyrrolidinyl (e.g., pyrrolidin-1-yl), morpholinyl (e.g.,         morpholin-4-yl),     -   d. “Aryl” as used herein is a mono or bicyclic aromatic         hydrocarbon (e.g., phenyl, naphthyl), preferably phenyl,         optionally substituted, e.g., with alkyl (e.g., methyl), halogen         (e.g., chloro or fluoro), haloalkyl (e.g., trifluoromethyl),         hydroxy, carboxy, or an additional aryl or heteroaryl (e.g.,         biphenyl or pyridylphenyl).     -   e. “Heteroaryl” as used herein is an aromatic moiety wherein one         or more of the atoms making up the aromatic ring is sulfur or         nitrogen rather than carbon, e.g., pyridyl, thiadiazolyl,         pyrrolyl (e.g., pyrrol-2-yl) or imidazolyl (e.g.,         1H-imidazol-2-yl), which may be optionally substituted, e.g.,         with alkyl, halogen, haloalkyl, hydroxy or carboxy.

PDE 1 Inhibitors may exist in free or salt form, e.g., as acid addition salts. In this specification unless otherwise indicated language such as PDE 1 Inhibitors is to be understood as embracing the compounds in any form, for example free or acid addition salt form, or where the compounds contain acidic substituents, in base addition salt form. The PDE 1 Inhibitors are intended for use as pharmaceuticals, therefore pharmaceutically acceptable salts are preferred. Salts which are unsuitable for pharmaceutical uses may be useful, for example, for the isolation or purification of free PDE 1 Inhibitors or their pharmaceutically acceptable salts.

PDE 1 Inhibitors may in some cases also exist in prodrug form, for example when the compounds contain physiologically hydrolysable and acceptable esters. As used herein, “physiologically hydrolysable and acceptable ester” means esters of PDE 1 Inhibitors which are hydrolysable under physiological conditions to yield acids (in the case of PDE 1 Inhibitors which have hydroxy substituents) or alcohols (in the case of PDE 1 Inhibitors which have carboxy substituents) which are themselves physiologically tolerable at doses to be administered. As will be appreciated the term thus embraces conventional pharmaceutical prodrug forms.

Methods of making and formulating the PDE 1 Inhibitors, novel intermediates useful for making PDE 1 Inhibitors, and methods of using the PDE 1 Inhibitors for treatment of diseases are generally disclosed in EP 0201188 (or U.S. Pat. No. 4,666,908) and EP 0911333 (or U.S. Pat. No. 6,235,742); PCT/US2006/022066; PCT/US2006/033179; WO 03/042216 (U.S. Pat. No. 6,943,171); U.S. Pat. No. 6,969,719; U.S. Pat. No. 5,939,419; EP 0 538 332 (U.S. Pat. No. 5,393,755); U.S. Pat. No. 5,393,755; U.S. Pat. No. 6,969,719 B2, Xia et al., J. Med. Chem. (1997), 40, 4372-4377 and Ahn et al., J. Med. Chem. (1997), 40, 2196-2210, the contents of all of which are incorporated herein by reference.

Methods of Treatment

The invention provides methods of treatment or prophylaxis of narcolepsy comprising administering an effective amount of a PDE 1 inhibitor, e.g., a PDE 1 Inhibitor as hereinbefore described, for example a Compound of any of Formulae I, Ia, II, III, IV, V, VI, VIIa, VIIb, VIIIa, VIIIb, IXa, IXb, X, XI or any of Formulae 1.2-1.17, 2.1-2.9, or 3.2-3.22, 4.1-4.17, 5.1-5.8, 6.1-6.1 or 7.1-7.12 to a human or animal patient, preferably a human, in need thereof.

PDE 1 Inhibitors may be used in the foregoing methods of treatment prophylaxis as a sole therapeutic agent, but may also be used in combination or for co-administration with other active agents. Thus, the invention further comprises a method of treating narcolepsy comprising administering simultaneously, sequentially, or contemporaneously administering therapeutically effective amounts of

-   -   (i) a PDE 1 Inhibitor, e.g., any of Formulae I, Ia, II, III, IV,         V, VI, VIIa, VIIb, VIIIa, VIIIb, IXa, IXb, X, XI or any of         Formulae 1.2-1.17, 2.1-2.9, 3.2-3.22, 4.1-4.17, 5.1-5.8, 6.1-6.2         or 7.1-7.12; and     -   (ii) a compound to promote wakefulness or regulate sleep, e.g.,         selected from (a) central nervous system stimulants-amphetamines         and amphetamine like compounds, e.g., methylphenidate,         dextroamphetamine, methamphetamine, and pemoline; (b)         modafinil, (c) antidepressants, e.g., tricyclics (including         imipramine, desipramine, clomipramine, and protriptyline) and         selective serotonin reuptake inhibitors (including fluoxetine         and sertraline); and/or (d) gamma hydroxybutyrate (GHB),         to a patient in need thereof.

The present invention also provides

(i) a PDE 1 Inhibitor for use in the treatment of any disease or condition as hereinbefore set forth, or in a method of treatment as hereinbefore set forth;

(ii) the use of a PDE 1 Inhibitor in the manufacture of a medicament for treating a disease or condition as hereinbefore set forth, or manufacture of a medicament for use in a method of treatment as hereinbefore set forth; and

(iii) a pharmaceutical composition comprising a PDE 1 Inhibitor in combination or association with a pharmaceutically acceptable diluent or carrier for use in the treatment of a disease or condition as hereinbefore set forth, or for use in a method of treatment as hereinbefore set forth.

The words “treatment” and “treating” are to be understood accordingly as embracing prophylaxis and treatment or amelioration of any of the symptoms of disease as well as treatment of the cause of the disease.

Dosages employed in practicing the present invention will of course vary depending, e.g. on the particular disease or condition to be treated, the particular PDE 1 Inhibitor used, the mode of administration, and the therapy desired. PDE 1 Inhibitors may be administered by any suitable route, including orally, parenterally, transdermally, or by inhalation, but are preferably administered orally. In general, satisfactory results, e.g. for the treatment of diseases as hereinbefore set forth are indicated to be obtained on oral administration at dosages of the order from about 0.01 to 2.0 mg/kg. In larger mammals, for example humans, an indicated daily dosage for oral administration will accordingly be in the range of from about 0.75 to 150 mg, conveniently administered once, or in divided doses 2 to 4 times, daily or in sustained release form. Unit dosage forms for oral administration thus for example may comprise from about 0.2 to 75 or 150 mg, e.g. from about 0.2 or 2.0 to 50, 75 or 100 mg of a PDE 1 Inhibitor, together with a pharmaceutically acceptable diluent or carrier therefor.

Pharmaceutical compositions comprising PDE 1 Inhibitors may be prepared using conventional diluents or excipients and techniques known in the galenic art. Thus oral dosage forms may include tablets, capsules, solutions, suspensions and the like.

EXAMPLES 1. Measurement of PDE1B Inhibition In Vitro Using IMAP Phosphodiesterase Assay Kit

Phosphodiesterase 1B (PDE1B) is a calcium/calmodulin dependent phosphodiesterase enzyme that converts cyclic guanosine monophosphate (cGMP) to 5′-guanosine monophosphate (5′-GMP). PDE1B can also convert a modified cGMP substrate, such as the fluorescent molecule cGMP-fluorescein, to the corresponding GMP-fluorescein. The generation of GMP-fluorescein from cGMP-fluorescein can be quantitated, using, for example, the IMAP (Molecular Devices, Sunnyvale, Calif.) immobilized-metal affinity particle reagent.

Briefly, the IMAP reagent binds with high affinity to the free 5′-phosphate that is found in GMP-fluorescein and not in cGMP-fluorescein. The resulting GMP-fluorescein-IMAP complex is large relative to cGMP-fluorescein. Small fluorophores that are bound up in a large, slowly tumbling, complex can be distinguished from unbound fluorophores, because the photons emitted as they fluoresce retain the same polarity as the photons used to excite the fluorescence.

In the phosphodiesterase assay, cGMP-fluorescein, which cannot be bound to IMAP, and therefore retains little fluorescence polarization, is converted to GMP-fluorescein, which, when bound to IMAP, yields a large increase in fluorescence polarization (Δmp). Inhibition of phosphodiesterase, therefore, is detected as a decrease in Δmp.

Enzyme Assay

Materials: All chemicals are available from Sigma-Aldrich (St. Louis, Mo.) except for IMAP reagents (reaction buffer, binding buffer, FL-GMP and IMAP beads), which are available from Molecular Devices (Sunnyvale, Calif.).

Assay: 3′,5′-cyclic-nucleotide-specific bovine brain phosphodiesterase (Sigma, St. Louis, Mo.) is reconstituted with 50% glycerol to 2.5 U/ml. One unit of enzyme will hydrolyze 1.0 μmole of 3′,5′-cAMP to 5′-AMP per min at pH 7.5 at 30° C. One part enzyme is added to 1999 parts reaction buffer (30 μM CaCl₂, 10 U/ml of calmodulin (Sigma P2277), 10 mM Tris-HCl pH 7.2, 10 mM MgCl₂, 0.1% BSA, 0.05% NaN₃) to yield a final concentration of 1.25 mU/ml. 99 μl of diluted enzyme solution is added into each well in a flat bottom 96-well polystyrene plate to which 1 μl of test compound dissolved in 100% DMSO is added. The compounds are mixed and pre-incubated with the enzyme for 10 min at room temperature.

The FL-GMP conversion reaction is initiated by combining 4 parts enzyme and inhibitor mix with 1 part substrate solution (0.225 μM) in a 384-well microtiter plate. The reaction is incubated in dark at room temperature for 15 min. The reaction is halted by addition of 60 μl of binding reagent (1:400 dilution of IMAP beads in binding buffer supplemented with 1:1800 dilution of antifoam) to each well of the 384-well plate. The plate is incubated at room temperature for 1 hour to allow IMAP binding to proceed to completion, and then placed in an Envision multimode microplate reader (PerkinElmer, Shelton, Conn.) to measure the fluorescence polarization (Δmp).

A decrease in GMP concentration, measured as decreased Δmp, is indicative of inhibition of PDE activity. IC₅₀ values are determined by measuring enzyme activity in the presence of 8 to 16 concentrations of compound ranging from 0.0037 nM to 80,000 nM and then plotting drug concentration versus ΔmP, which allows IC₅₀ values to be estimated using nonlinear regression software (XLFit; IDBS, Cambridge, Mass.). 

1. A method of treatment or prophylaxis for narcolepsy comprising administering an effective amount of a PDE 1 inhibitor to a patient in need thereof.
 2. The method of claim 1 wherein the PDE 1 inhibitor is a compound of the formula (I):

wherein (i) R₁ is H or C₁₋₄ alkyl; (ii) R₄ is H or C₁₋₄ alkyl and R₂ and R₃ are, independently, H or C₁₋₄ alkyl, aryl, heteroaryl, heteroarylalkoxy, arylalkoxy, heteroarylalkyl, or arylalkyl; or R₂ is H and R₃ and R₄ together form a di-, tri-, or tetra-methylene bridge; (iii) R₅ is a substituted heteroarylalkyl, or R₅ is attached to one of the nitrogen atoms on the pyrazolo portion of Formula I and is a moiety of Formula Q

wherein X, Y and Z are, independently, N or C; R₈, R₉, R₁₁ and R₁₂ are independently H or halogen; and R₁₀ is halogen, alkyl, cycloalkyl, haloalkyl, aryl, heteroaryl, or thiadiazolyl, diazolyl, triazolyl, tetrazolyl, arylcarbonyl, alkylsulfonyl, heteroarylcarbonyl, or alkoxycarbonyl; provided that when X, Y, or Z is nitrogen, R₈, R₉, or R₁₀, respectively, is not present; (iv) R₆ is H, alkyl, aryl, heteroaryl, arylalkyl, arylamino, heterarylamino, N,N-dialkylamino, N,N-diarylamino, or N-aryl-N-(arylalkyl)amino; and (v) n=0 or 1; (vi) when n=1, A is —C(R₁₃R₁₄)— wherein R₁₃ and R₁₄, are, independently, H or C₁₋₄ alkyl, aryl, heteroaryl, heteroarylalkoxy, arylalkoxy, heteroarylalkyl or arylalkyl; in free, pharmaceutically acceptable salt or prodrug form.
 3. The method according to claim 1, wherein the PDE 1 inhibitor is a compound of Formula II:

wherein R_(a) and R_(b) are, independently, H or C₁₋₄ alkyl; R₆ is phenylamino or benzylamino; R₁₀ is phenyl, pyridyl, or thiadiazolyl; in free or pharmaceutically acceptable salt form.
 4. The method according to claim 1 wherein the PDE 1 inhibitor is a compound of Formula III:

wherein R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene bridge; or at least one of R₂ and R₃ is methyl, isopropyl or arylalkoxy and R₄ is H; or R₂ and R₃ are H and R₄ is a C₁₋₄ alkyl; R₆ is phenylamino or benzylamino; R₁₀ is haloalkyl, phenyl, pyridyl, or thiadiazolyl; in free or pharmaceutically acceptable salt form.
 5. The method according to claim 1 wherein the PDE 1 inhibitor is a compound of Formula IV:

wherein R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene bridge; or at least one of R₂ and R₃ is methyl, isopropyl or arylalkoxy and R₄ is H; or R₂ and R₃ are H and R₄ is a C₁₋₄ alkyl; R₆ is phenylamino or benzylamino; R₁₀ is phenyl, pyridyl, or thiadiazolyl; in free or pharmaceutically acceptable salt form.
 6. The method according to claim 1 wherein the PDE 1 inhibitor is a compound of formula Ia:

wherein (i) R₁ is H or C₁₋₄ alkyl; (ii) R₄ is H and R₂ and R₃ are, independently, H or C₁₋₄ alkyl, aryl, or arylalkyl; or R₂ is H and R₃ and R₄ together form a di-, tri- or tetramethylene bridge; (iii) R₅ is attached to one of the nitrogens on the pyrazolo portion of formula I and is a substituted benzyl of formula Qa

wherein R₈, R₉, R₁₁ and R₁₂ are independently H or halogen; and R₁₀ is halogen, alkyl, cycloalkyl, haloalkyl, aryl, heteroaryl, arylcarbonyl, alkyl sulfonyl or heteroarylcarbonyl, and (iv) R₆ is H, alkyl, aryl, heteroaryl, arylalkyl, arylamino, heteroarylamino, arylalkylamino, N,N-dialkylamino, N,N-diarylamino, or N-aryl-N-(arylalkyl)amino; in free, pharmaceutically acceptable salt or prodrug form.
 7. The method according to claim 1 wherein the PDE 1 inhibitor is a compound of Formula V:

wherein R₂ is H and R₃ and R₄ together form a tri- or tetra-methylene bridge; or R₂ and R₃ are each methyl and R₄ is H; or R₂ and R₄ are H and R₃ is isopropyl; R₆ is phenylamino or benzylamino; R₁₀ is phenyl, pyridyl, or thiadiazolyl; in free or pharmaceutically acceptable salt form.
 8. The method of claim 1 wherein the PDE 1 inhibitor is a compound of the Formula (VI)

wherein R_(a) is methyl or C₂-C₆ alkyl; R₁ is H or C₁-C₄ alkyl; each of R₂ and R₃ is independently selected from H and C₁-C₄ alkyl, or R₂ is H or C₁-C₄ alkyl and R₃ is OH, C₂-C₄ alkanoyloxy or fluoro, or R₂ and R₃ when taken together represent C₂-C₆ alkylene, or R₂ and R₃ when taken together with the carbon atom to which they are attached represent a carbonyl group; Ar is either (a)

wherein each of R₄, R₅ and R₆ is independently selected from H C₁-C₄ alkyl, C₁-C₄ alkoxy, C₁-C₄ alkoxy-Z-, halo, halo(C₁-C₄)alkyl, phenoxy, optionally substituted by up to three substitutents each of which substitutent is independently selected from halo, C₁₋₄ alkyl, and C₁-C₄ alkoxy, nitro, hydroxy, hydroxy-Z-, C₂-C₄ alkanoyl, amino, amino-Z-, (C₁-C₄ alkyl)NH, (C₁-C₄ alkyl)₂N—, (C₁-C₄ alkyl)NH—Z—, (C₁-C₄ alkyl)₂N—Z—, —COOH, —Z—COOH, —COO(C₁-C₄ alkyl), —Z—COO(C₁-C₄ alkyl) C₁-C₄ alkanesulphonamido, C₁-C₄ alkanesulphonamido-Z-, halo(C₁-C₄)alkanesulphonamido, halo(C₁-C₄)alkanesulphonamido-Z-, C₁-C₄ alkanamido, C₁-C₄ alkanamido-Z-, HOOC—Z—NH—, HOOC—Z—NH—Z—, (C₁-C₄ alkyl)OOC—Z—NH—, (C₁-C₄ alkyl)OOC—Z—NH—Z—, C₁-C₄ alkyl-NH—SO₂—NH—, C₁-C₄ alkyl-NH—SO₂—NH—Z—, (C₁-C₄ alkyl)₂-N—SO₂—NH—, (C₁-C₄ alkyl)₂-N—SO₂—NH—Z—, C₁-C₄ alkoxy CH═CH—Z—CONH—, C₁-C₄ alkoxy CH═CHCONH C₁-C₄ alkyl-SO₂—N(C₁-C₄ alkyl)-, C₁-C₄ alkyl-SO₂—N(C₁-C₄ alkyl)-Z-, (C₁-C₄ alkyl)NH—Z—SO₂—NH—, (C₁-C₄ alkyl)₂N—Z—SO₂—NH—, (C₁-C₄ alkyl)NH—Z—SO₂—NH—Z—, (C₁-C₄ alkyl)₂N—Z—SO₂—NH—Z—, benzenesulphonamido, optionally ring substituted by up to three substitutents each of which is independently selected from halo, C₁₋₄ alkyl, and C₁-C₄ alkoxy, C₁-C₄ alkanoyl-N(C₁-C₄ alkyl)-, C₁-C₄ alkanoyl-N(C₁-C₄ alkyl)-Z-, C₁-C₄ alkoxycarbonyl-CH(CH₂OH)NHSO₂—, —SO₃H, —SO₂NH₂, H₂NOC—CH(CH₂OH)—NHSO₂—, HOOC—Z—O—, and (C₁-C₄ alkyl)OOC—Z—O—, or optionally one of R₄, R₅ and R₆ is a G-Het group and wherein the others of R₄, R₅ and R₆ are independently selected from the R₄, R₅ and R₆ substitutents listed above; Z is C₁-C₄ alkylene, G is a direct link, Z, O, —SO₂NH—, SO₂, or —Z—N(C₁-C₄ alkyl)SO₂—, Het is a 5- or 6-membered heterocyclic group containing 1, 2, 3 or 4 nitrogen heteroatoms; or 1 or 2 nitrogen heteroatoms and 1 sulphur heteroatom or 1 oxygen heteroatom; or the heterocyclic group is furanyl or thiophenyl; wherein the Het group is saturated or partially or fully unsaturated and optionally substituted by up to 3 substitutents, wherein each substitutent is independently selected from C₁-C₄ alkyl, oxo, hydroxy, halo, and halo(C₁-C₄) alkyl; or (b) any one of the following bicyclic groups: benzodioxolanyl, benzodioxanyl, benzimidazolyl, quinolinyl, indolyl, quinazolinyl, isoquinolinyl, benzotriazolyl, benzofuranyl, benzothiophenyl, quinoxalinyl, or phthalzinyl, wherein said bicyclic Ar groups are linked to the neighbouring —C(R₂R₃)— group via the benzo ring portion, and wherein the heterocyclic portion of said bicyclic Ar group is optionally partially or fully saturated, said group being optionally substituted by one or more of C₁-C₄ alkyl, halo, hydroxy, oxo, amino, and C₁-C₄ alkoxy; in free or pharmaceutically acceptable salt form.
 9. The method according to claim 1 wherein the PDE 1 inhibitor is selected from the following:

in free or pharmaceutically acceptable salt form.
 10. The method according to claim 1 wherein the PDE 1 inhibitor is

in free or pharmaceutically acceptable salt form.
 11. The method according to claim 1 wherein the PDE 1 inhibitor is a compound of the Formula VIIIa or VIIb:

in free or pharmaceutically acceptable salt form, wherein: i) q=0, 1 or 2; ii) R¹, R^(a), R^(b), R^(c) and R^(d) are each independently H, alkyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl groups, wherein each alkyl group of R¹, R^(a), R^(b), R^(c) and R^(d) is independently unsubstituted or substituted with 1 to 5 independently selected R³ moieties which can be the same or different, each R³ moiety being independently selected from the group consisting of hydroxy, alkoxy, cycloalkoxy, aryloxy, alkylthio, arylthio, aryl, haloaryl, heteroaryl, cycloalkyl, heterocycloalkyl, amino, alkylamino, dialkylamino, cycloalkylamino and heterocycloalkylamino groups; wherein each of the aryl, heteroaryl, cycloalkyl and heterocycloalkyl groups of R¹, R^(a), R^(b), R^(c) and R^(d) is independently unsubstituted or substituted with 1 to 5 independently selected R⁴ moieties which can be the same or different, each R⁴ moiety being independently selected from the group consisting of halo, optionally substituted aryl, heteroaryl, nitro, cyano, haloalkyl, haloalkoxy, alkyl, alkoxy, cycloalkyl, heterocycloalkyl, cycloalkylalkyl, amino, alkylamino, dialkylamino, —OCF₃, acyloxy, —OR⁸, —C(O)R⁹, —C(O)OR⁸, —NR¹⁰C(O)R⁹, —NR¹⁰C(O)OR⁸, —NR¹⁰S(O)₂R⁹, —S(O)₀₋₂R⁹ groups, carbonyl when two hydrogens attached to the same carbon atom of the cycloalkyl or heterocycloalkyl group of R′ are substituted, and ═CR⁸R⁹ when two hydrogens attached to the same carbon atom of the cycloalkyl or heterocycloalkyl groups of R¹ are substituted, wherein each of the aryl, heteroaryl, cycloalkyl and heterocycloalkyl groups of the R³ and R⁴ moieties above is independently unsubstituted or substituted with 1 to 5 independently selected R¹² moieties which can be the same or different, each R¹² moiety being independently selected from the group consisting of: halo, phenyl, nitro, cyano, haloalkyl, haloalkoxy, alkyl, cycloalkyl, cycloalkylalkyl, amino, alkylamino, —OCF₃, acyloxy, —OR⁸, —C(O)R⁹, —C(O)OR⁸, —NR¹⁰C(O)R⁹, —NR¹⁰C(O)OR⁸, —NR¹⁰S(O)₂R⁹, —S(O)₀₋₂R⁹ groups, carbonyl when two hydrogens attached to the same carbon atom of the cycloalkyl or heterocycloalkyl group of R³ or R⁴ are substituted, and ═CR⁸R⁹ when two hydrogens attached to the same carbon atom of the cycloalkyl or heterocycloalkyl group of R³ or R⁴ are substituted; or iii) R^(a) and R^(b), together with the carbon to which they are both attached, form a 4- to 7-membered cycloalkyl or heterocycloalkyl ring, and R^(c) and R^(d) are each independently H or an alkyl group; or iv) R^(a) and R^(c), together with the respective carbons to which they are attached, form a 4- to 7-membered cycloalkyl or heterocycloalkyl ring, and R^(b) and R^(d) are each independently H or an alkyl group, preferably R^(a) and R^(c) together have the cis configuration, e.g., where the carbons carrying R^(a) and R^(c) have the R and S configurations, respectively; v) R² is H, halo, alkyl, haloalkyl, alkoxy, alkylthio, amino, aminosulfonyl, monoalkylamino, dialkylamino, hydroxyalkylamino, aminoalkylamino, carboxy, alkoxycarbonyl, aminocarbonyl or alkylaminocarbonyl group, wherein each alkyl group of R² is independently unsubstituted or substituted with 1 to 5 independently selected R¹³ moieties which can be the same or different, each R¹³ moiety being independently selected from the group consisting of halo, hydroxy, alkoxy, alkyl, aryl, heteroaryl, cycloalkyl, heterocycloalkyl, amino, monoalkylamino or dialkylamino group, wherein each aryl group of R¹³ is independently unsubstituted or substituted with 1 to 5 independently selected R⁴ moieties which can be the same or different; vi) Y is H or an alkyl group substituted with (i) an aryl, heteroaryl, cycloalkyl, hydroxy, alkoxy, amino, monoalkylamino or dialkylamino group, or (ii) an aryl group substituted with from one to three moieties each independently selected from the group consisting of: halo, alkyl, phenyl, hydroxy, alkoxy, phenoxy, amino, monoalkylamino and dialkylamino group; vii) each R⁸ is independently H, alkyl or aryl; viii) each R⁹ is independently H, alkyl, aryl or —NR¹⁰R¹¹; ix) each R¹⁰ is independently H, alkyl, aryl, heteroaryl, arylalkyl or heteroarylalkyl, wherein each alkyl, aryl, heteroaryl, arylalkyl or heteroarylalkyl of R¹⁰ is unsubstituted or independently substituted with 1 to 5 R¹⁴ moieties which can be the same or different, each R¹⁴ moiety being independently selected from the group consisting of: halo, alkyl, aryl, cycloalkyl, —CF₃, —OCF₃, —CN, —OR⁸, —CH₂OR⁸, —C(O)OR⁸ and —C(O)NR⁸R⁸; and x) each R¹¹ is independently H, alkyl, aryl, heteroaryl, arylalkyl or heteroarylalkyl, wherein each alkyl, aryl, heteroaryl, arylalkyl or heteroarylalkyl of R¹¹ is unsubstituted or independently substituted with 1 to 5 R¹⁴ moieties which can be the same or different.
 12. The method according to claim 1, wherein the PDE 1 inhibitor is selected from the following:

in free or pharmaceutically acceptable salt form.
 13. The method according to claim 1, wherein the PDE 1 inhibitor is

in free or pharmaceutically acceptable salt form.
 14. The method according to claim 1, wherein the PDE 1 inhibitor is a compound of Formula VIIIa or VIIIb:

in free or pharmaceutically acceptable salt form, wherein: J is oxygen or sulfur, R¹ is hydrogen, alkyl or alkyl substituted with aryl or hydroxy; R² is hydrogen, aryl, heteroaryl, cycloalkyl, alkyl or alkyl substituted with aryl, heteroaryl, hydroxy, alkoxy, amino, monoalkyl amino or dialkylamino, or —(CH₂)_(m)TCOR²⁰ wherein m is an integer from 1 to 6, T is oxygen or —NH— and R²⁰ is hydrogen, aryl, heteroaryl, alkyl or alkyl substituted with aryl or heteroaryl; R³ is hydrogen, halo, trifluoromethyl, alkoxy, alkylthio, alkyl, cycloalkyl, aryl, aminosulfonyl, amino, monoalkylamino, dialkylamino, hydroxyalkylamino, aminoalkylamino, carboxy, alkoxycarbonyl or aminocarbonyl or alkyl substituted with aryl, hydroxy, alkoxy, amino, monoalkylamino or dialkylamino; R^(a), R^(b), R^(c) and R^(d) independently represent hydrogen, alkyl, cycloalkyl or aryl; or (R^(a) and R^(b)) or (R^(c) and R^(d)) or (R^(b) and R^(c)) can complete a saturated ring of 5- to 7-carbon atoms, or (R^(a) and R^(b)) taken together and (R^(b) and R^(c)) taken together, each complete a saturated ring of 5- to 7-carbon atoms, wherein each ring optionally can contain a sulfur or oxygen atom and whose carbon atoms may be optionally substituted with one or more or the following: alkenyl, alkynyl, hydroxy, carboxy, alkoxycarbonyl, alkyl or alkyl substituted with hydroxy, carboxy or alkoxycarbonyl; or such saturated ring can have two adjacent carbon atoms which are shared with an adjoining aryl ring; and n is zero or one.
 15. The method according to claim 14, wherein the PDE 1 inhibitor is a compound of Formula VIIIa or VIIIb selected from a group consisting of: cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(phenylmethyl)cyclopenta[4,5]imidazo-[2,1-b]purin-4-one; 7,8-Dihydro-5-methyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one; 5,7,8,9-Tetrahydro-5-methyl-3-(phenylmethyl)pyrimido[2,1-b]purin-4(3H)-one; 7,8-Dihydro-8-phenyl-5-methyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 5′,7′-Dihydro-5′-methyl-3′-(phenylmethyl)spiro[cyclohexane-1,8′-(8H)imidazo-[2,1-b]purin]4′(3′H)-one; cis-5,6a,11,11a-Tetrahydro-5-methyl-3-(phenylmethyl)indeno[1′,2′:4,5]imidazo-[2,1-b]purin-4(3H)-one; 5′,7′-Dihydro-2′,5′dimethyl-3′-(phenylmethyl)spiro{cyclohexane-1,7′(8′H)-imidazo[2,1-b]purin}-4′-(3′H)-one; 7,8-Dihydro-2,5,7,7,8(R,S)-pentamethyl-3H-imidazo[2,1-b]purin-4(5H)-one; cis-5,6a,7,11b-Tetrahydro-5-methyl-3-(phenylmethyl)indeno[2′,1′,:4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4-(3H)-one; 5′-Methyl-3′-(phenylmethyl)-spiro[cyclopentane-1,7′-(8′H)-(3′H)imidazo[2,1-b]purin]-4-(5′H)-one; 7,8-Dihydro-2,5,7,7-tetramethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5′H)-one; 7,8-Dihydro-7(R)-phenyl-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-3,7(R)-bis(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; (±)-7,8-Dihydro-2,5-dimethyl-7-ethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 6a(S)-7,8,9,10,10a(R)-Hexhydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one; 6a(R)-7,8,9,10,10a(S)-hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo-[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(R)-isopropyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5,7(R)-trimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; cis-7,7a,8,9,10,10a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-cyclopenta-[5,6]pyrimido[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylpropyl)-3-(phenylmethyl)-3H-imidazo-[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(R)-(2-methylpropyl)-3-(phenylmethyl)-3H-imidazo-[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(R,S)-(methoxycarbonyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(R,S)-(1-propyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylethyl)-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5,7,7,8(R,S)-pentamethyl-3H-imidazo[2,1-b]purin-4(5H)-one; 5,7,8,9-Tetrahydro-2,5,7,9(R,S)-pentamethyl-3-(phenylmethyl)-pyrimido[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(S),7,8,9,9a(R)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-6a,7,8,9,10,10a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one; 5′,7′-Dihydro-2′,5′-dimethyl-3′-(phenylmethyl)spiro[cyclohexane-1,8-(8H)-imidazo[2,1-b]purin]-4-(3′H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclohept-[6,7]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4-(5H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-ethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-phenyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-6a,7,8,9,10,10a-Hexahydro-5-methyl-2-phenyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methylcyclopenta[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2,5-dimethylcyclopenta[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a(R), 7,8,9,9a(S)-Hexahydro-2,5-di-methylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; 2′,5′-dimethyl-spiro{cyclopentane-1,7′-(8′H)-(3′H)-imidazo[2,1-b]purin}-4′(5′H)-one; 7,8-Dihydro-2,5-dimethyl-7(R)-(1-methylethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5,7,7-tetramethyl-3H-imidazo[2,1-b]purin-4(5H)-one; 7,8-Dihydro-2,5-dimethyl-7(S)-(1-methylethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; 6a(R),7,8,9,10,10a(S)-Hexahydro-2,5-dimethyl-3H-benzimidazo[2,1-b]purin-4(5H)-one; 5′,7′-Dihydro-2′,5′-dimethylspiro{cyclohexane-1,7-(8′H)-imidazo[2,1-b]purin}-4′(3′H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(phenylmethyl)cyclopenta[4,5]-imidazo[2,1-b]purin-4(3H)-thione; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-thione; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(4-chlorophenylmethyl)cyclopenta[4,5]-imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(cyclohexylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-3-(2-naphthylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-bromophenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(R)-7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-methoxyphenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2,3,5-trimethylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2-(hydroxymethyl)-5-methyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2-methylthio-5-methyl-3-(Phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-3,4,5,6a,7,8,9,9a-Octahydro-5-methyl-4-oxo-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-2-carboxylic acid; cis-3,4,5,6a,7,8,9,9a-Octahydro-5-methyl-4-oxo-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-2-carboxylic acid, methyl ester; cis-5,6a,7,8,9,9a-Hexahydro-2-bromo-5-methyl-3-(phenylmethyl)cyclopent[4,5]imidazo[2,1-b]purin-4(3H)one; cis-5,6a,7,8,9,9a-Hexahydro-2-(methylaminosulfonyl)-5-methyl-3-(phenylmethyl)cyclopent[4,5]imidazo[2,1-b]purin-4(3H)one; cis-1-Cyclopentyl-5,6a,7,8,9,9a-hexahydro-5-methylcyclopent[4,5]imidazo[2,1-b]purin-4-(1H)one; cis-5,6a,7,8,9,9a-Hexahydro-3,5-bis-(phenylmethyl)cyclopent(4,5)imidazo[2,1-b]purin-4(3H)one; cis-6a,7,8,9,10,10a-Hexahydro-3,5-bis-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)one; cis-3-Cyclopentyl-5,6a,7,8,9,9a-hexahydro-5-methylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)one; 5′-Methyl-3′-(phenylmethyl)spiro[cyclopentane-1,7-(8′H)-(3′H)imidazo[2,1-b]purin]-4-(5H)one; 2′,5′-Dimethyl-3′-(phenylmethyl)-spiro[cyclopentane-1,7-(8′H)-(3H)imidazo[2,1-b]purin]-4-(5′H)one; cis-5,6a,(R)7,8,9,9a(S)-Hexahydro-5-methyl-3-(phenylmethyl)cyclopent[4,5]-imidazo[2,1-b]purin-4(3H)one; cis-3-Cyclopentyl-5,6a,7,8,9,9a-Hexahydro-2,5-dimethylcyclopent[4,5]imidazo-[2,1-b]purin-4(3H)one; 5′-Methyl-2′-trifluoromethyl-3′-(phenylmethyl)spiro{cyclo-pentane-1,7′(8′H)-(3′H)imidazo[2,1-b]purin}-4-(5′H)-one; 7,8-Dihydro-5,7,7-trimethyl-2-trifluoromethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(5H)-one; (+/−)-cis-5,6a,7,8,9,9a-Hexahydro-5-methyl-2-trifluoromethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; (+/−)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-(phenylmethyl)-3H-pentaleno[6a′,1′:4,5]imidazo[2,1-b]purin-4(5H)-one; (+)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-phenylmethyl-3H-pentaleno[6a′,1′:4,5]imidazo[2,1-b]purin-4(5H)-one; (−)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3-phenylmethyl-3H-pentaleno[6a′,1′:4,5]Imidazo[2,1-b]purin-4(5H)-one; (+/−) 6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one; (+)-6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one; (+6a,7,8,9,9a,10,11,11a-Octahydro-2,5-dimethyl-3H-pentaleno[6a′,1′:4,5]-imidazo[2,1-b]purin-4(5H)-one; 6a,7,8,9,10,10a,11,12,13,13a-Decahydro-2,5-dimethyl-(3-phenylmethyl)-napth[1,8a-d]imidazo[2,1-b]purin-4(5H)one; 7(R)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(3H)-one; 7(R)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3H-imidazo[2,1-b]purin-4(5H)-one; 7(S)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3-(phenylmethyl)-3H-imidazo[2,1-b]purin-4(3H)-one; 7(S)-Cyclohexyl-7,8-dihydro-2,5-dimethyl-3H-imidazo[2,1-b]purin-4(5H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-[3-(trimethylacetoxy)methyl]-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-(4-pyridylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-[2-(4-morpholinyl)-ethyl]cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5-dimethyl-3-[acetoxymethyl]cyclopent-[4,5]imidazo[2.1-b]purin-4(3H)-one; 5,6a,7,8,9,9a-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)cyclopent-[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(R),7,8,9,9a(S)-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; 5,6a(S),7,8,9,9a(R)-Hexahydro-2,5,6a-trimethyl-3-(phenylmethyl)-cyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; cis-6a,7,8,9,10,10a-Hexahydro-2,5,7-trimethyl-3-(phenylmethyl)-3H-benzimidazo[2,1-b]purin-4(5H)-one; cis-5,6a,7,8,9,9a-Hexahydro-2,5,6a-trimethylcyclopent[4,5]imidazo[2,1-b]purin-4(3H)-one; or cis-[6a,7,8,9,10,10a-Hexahydro-2,5,7-trimethyl-3H-benzimidazo[2,1-b]purin-4(5H)-one]. in free or pharmaceutically acceptable salt form.
 16. The method according to claim 1, wherein the PDE 1 Inhibitor is a Compounds of Formula IXa or IXb:

in free or pharmaceutically acceptable salt form, wherein, q=0 or 1; R₁ is H, cycloalkyl, alkyl, R²³-alkyl- or R²⁶; R^(a), R^(b) and R^(c) are, independently of one another, each H, alkyl, cycloalkyl, aryl, R²²-aryl- or R²⁴-alkyl-; or R^(a) and R^(b), together with the carbon to which they are both attached, form a 4- to 7-membered ring, and R^(c) is H or alkyl; or R^(a) and R^(c), together with the respective carbons to which they are attached, form a 4- to 7-membered ring, and R^(b) is H or alkyl; (i) X is a bond; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is monohaloalkyl, polyhaloalkyl, provided that it is not trifluoromethyl, azido, cyano, oximino, cycloalkenyl, heteroaryl, R²²-heteroaryl- or R²⁷-alkyl-; (ii) X is a bond; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is H, halo, —CONHR⁶, —CONR⁶R⁷, —CO₂R⁶, monohaloalkyl, polyhaloalkyl, azido, cyano, —C═N—OR⁶, cycloalkyl, cycloalkylalkyl, R²⁶, aminosulfonyl, alkyl or R²³-alkyl- (iii) X is —O— or —S—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is R²⁶, cycloalkyl cycloalkylalkyl, heterocycloalkyl, cycloalkenyl or R²⁶-alkyl-; (iv) X is —O— or —S—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, cycloalkenyl or R²⁸-alkyl-; (v) X is —SO— or —SO₂—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, cycloalkenyl or R²⁸-alkyl-; (vi) X is —NR⁸—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is (R²⁹)_(p)-alkyl-, cycloalkyl, (R³⁰)_(p)-cycloalkyl-, cycloalkenyl, (R³⁰)_(p)-cycloalkenyl-, heterocycloalkyl or (R³⁹)_(p)-heterocycloalkyl-: (vii) X is —NR⁸—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, cycloalkenyl or R³¹-alkyl-; or (viii) X is —C≡C—; Y is aryl-alkyl or R²²-aryl-alkyl-; and R² is alkyl, R²⁶, cycloalkyl, cycloalkylalkyl or R²³-alkyl-; where, R⁶ is H or R⁷; R⁷ is alkyl, cycloalkyl or cycloalkylalkyl; R⁸ is heterocycloalkyl or R⁶; R²¹ is 1-6 substituents each independently selected from the group consisting of halo, hydroxy, alkoxy, phenoxy, phenyl, nitro, aminosulfonyl, cyano, monohaloalkyl, polyhaloalkyl, thiol, alkylthio, cycloalkyl, cycloalkylalkyl, amino, alkylamino, acylamino, carboxyl, —C(O)OR³⁴, carboxamido, —OCF₃ and acyloxy; R²² is 1-6 substituents each independently selected from the group consisting of alkyl and R²¹; R²³ is cycloalkoxy aryloxy, alkylthio, arylthio, cycloalkyl or R²⁸; R²⁴ is cycloalkyl or R²⁶; R²⁵ is hydroxy, alkoxy, amino, monoalkylamino, dialkylamino or R²⁶; R²⁶ is aryl, R²²-aryl 1, heteroaryl or R²²-heteroaryl-; R²⁷ is cycloalkoxy, aryloxy, alkylthio, arylthio, heteroaryl, R²²-heteroaryl-, cycloalkyl, heterocycloalkyl, cycloalkenyl, cycloalkylamino or heterocycloalkylamino; R²⁸ is cycloalkylamino, heterocycloalkylamino or R²⁵; R²⁹ is alkoxy, cycloalkylamino, heterocycloalkylamino or R²⁶; R³⁰ is halo, hydroxy, alkoxy, amino, aminosulfonyl, cyano, monohaloalkyl, polyhaloalkyl, thiol, alkylthio, alkyl, cycloalkyl, cycloalkylalkyl or acyloxy; R³¹ is cycloalkyl or R²⁸; R³⁴ is alkyl, aryl, aralkyl and heteroaryl; and p is 1 to
 4. 17. The method according to claim 1, wherein the PDE 1 inhibitor is a Compound of Formula X:

in free or a pharmaceutically acceptable salt form, wherein: R₁, R₂ and R₃ are independently selected from the group consisting of hydrogen, lower alkyl, lower alkoxy, halogeno, hydroxy, (di-lower alkyl)amino, 4-morpholinyl, 1-pyrrolidinyl, 1-pyrrolyl, —CF₃, —OCF₃, phenyl and methoxyphenyl; or R₁ and R₂ together are methylenedioxy; or R₁ and R₂ together with the carbon atoms to which they are attached form a benzene ring; and R^(a) is hydrogen and R^(b) and R^(c), together with the carbon atoms to which they are attached, form a saturated ring of 5 carbons; or R^(a) is lower alkyl, R^(b) is hydrogen or lower alkyl, and R^(c) is hydrogen; or R^(a), R^(b) and the carbon atom to which they are attached form a saturated ring of 5-7 carbons, and R^(c) is hydrogen; or R^(a) is hydrogen, and R^(b), R^(c) and the carbon atoms to which they are attached form a tetrahydrofuran ring; or R^(a) and R^(b), together with the carbon atom to which they are attached, and R^(b) and R^(c), together with the carbon atoms to which they are attached, each form a saturated ring of 5-7 carbons.
 18. The method of claim 1, wherein the PDE 1 inhibitor is a Compound selected from:

in free or pharmaceutically acceptable salt form.
 19. The method according to claim 1, wherein the PDE 1 inhibitor inhibits phosphodiesterase-mediated hydrolysis of cGMP or cAMP.
 20. The method according to claim 1, wherein the PDE1 inhibitor is a PDE1B inhibitor.
 21. The method according to claim 1 further comprising administering a compound or compounds selected from central nervous system stimulants, modafinil, antidepressants, and gamma hydroxybutyrate.
 22. (canceled)
 23. (canceled)
 24. (canceled)
 25. The method according to claim 1 wherein the PDE 1 inhibitor is:

in free or pharmaceutically acceptable salt form. 